People have been getting high for a long time, likely pre-dating the earliest civilizations by thousands of years. It’s a natural human experience to alter consciousness. From the socially acceptable sugar, coffee, and alcohol to the more adventurous MDMA, magic mushrooms, LSD, ayahuasca, and countless other entheogenic plant and chemical preparations, humans trip. It’s a part of life.
Cannabis has long been used as a tool for expanding consciousness. Ancient incense burners in China used in funeral rites have been cited as the first documentation of the plant for psychoactive use, some 2,700 years ago.  Around 1,000 years before that on the Indian subcontinent, schools of tantric and kundalini yoga ate large amounts of cannabis before ceremonies to come closer to connection to the universe and the self.  There’s strong evidence that people were using cannabis to get high before they used it as a medicine (even though they go hand in hand), and that psychoactive use preceded the cultivation of hemp for food and textiles.
Another strong example of the targeted use of cannabis for psychoactivity was the Club des Hashischins in Paris circa the 19th century. This group of hashish eaters rebelled against the bourgeois moral code and dedicated themselves to exploring drug-induced experiences. Prominent French artists, writers, and scientists such as Alexandre Dumas, Victor Hugo, and Charles Baudelaire attended for creative curiosity. The bouquet of terpenes from cannabis was called a “riot of perfumes” by poet and hash-eater Arthur Rimbaud. What transpired created some of the greatest contributions to art in the history of the country. These club members inspired cannabis related studies, produced important works of art, and popularized drug imagery in literature. [3,4]
The modern use of cannabis undoubtedly includes it as a tool for getting high. Some folks gravitate to the plant for exactly that purpose. “Stoner Culture” is hailed as the recreational side of the cannabis industry, often depicted in songs, movies, and popular culture. Yet cannabis can also grant medicinal uses without much psychoactive effect. How does cannabis cause (and not cause) a high? Does its ability to enhance visual, auditory, and sensational experience warrant a definition of it as a “psychedelic”?
Our vastly resourceful online friend Wikipedia defines psychedelics as “a class of drug whose primary action is to trigger psychedelic experiences via serotonin receptor agonism, causing thought and visual/auditory changes, and altered state of consciousness.” This is different than an entheogen, which is a preferred term in some circles. It means: “a class of psychoactive substances that induce any type of spiritual experience aimed at development or sacred use.” The term entheogen is often used to contrast from the recreational use of the same drugs. And finally, the well known and somewhat out-of-style term of hallucinogen: “a psychoactive agent which most likely causes hallucinations, perceptual anomalies, and other substantial subjective changes in thoughts, emotion, and consciousness.”
Based on these definitions, we can classify cannabis as a psychedelic/entheogen/hallucinogen, which makes it stand out from other chemical and natural tools for consciousness expansion. Cannabis can induce visual and auditory changes. For example, ever notice how music is that much better when under the influence of the plant? Cannabis alters consciousness for its ability to relieve anxiety and stress for certain individuals, and sometimes causing paranoia in others. 
Cannabis is entheogenic because it has been used by folks throughout history as a tool for ritual and connection to the divine.  And for anyone who has taken too much of a cannabis edible, had an “out of body experience”, gotten the spins, or smoked weed for the first time and thought they saw elves, could potentially define the plant as hallucinogenic.
But cannabis can also be non-psychoactive, which is where it gets tricky.
What makes us “trip”? The answer is as complex as the varied receptors we have throughout our body. When discussing psychoactivity and a psychedelic experience, some key receptor channels come into play. For example, the hallucinations caused by some substances are due to these drugs imitating serotonin, a chemical messenger in our brains known to make us “feel good”. The human brain has numerous serotonin receptors which all play a role in our mood and senses. For example, serotonin is released during an experience with the drug MDMA (“Ecstasy”) which gives users a feeling of love and connection to others. 
Cannabinoids, some of the principle active components in the cannabis plant, interact with the endocannabinoid system and other receptor channels. Cannabinoid receptor 1 (CB1) sites are located throughout the brain and nervous system. CB1 is responsible for mediating pain perception, memory, mood, and motor function depending on where in the body they are located. It also causes the “high” experience of cannabis, since substances that directly bind to this receptor produce psychoactive effects. 
Cannabis contains compounds that both produce and mitigate psychoactivity. The infamous “non psychoactive” cannabinoid taking the world by storm, CBD, actually acts on serotonin receptors which is a hallmark characteristic of a psychedelic substance. But it is also commonly accepted as being non-intoxicating by most people. How can that be?
CBD has little binding affinity for the cannabinoid receptors CB1 and CB2, yet cannabidiol fastens itself directly to 5-HT1 and 5-HT2, two distinct serotonin receptor binding sites. The 5-HT2A receptor, known as the psychedelic receptor, also moderates the effects of mescaline, LSD, and other psychedelic substances. Yet LSD and CBD bind to 5-HT2A in distinct manners. The result is that these compounds produce widely different effects. 
The reason for this is believed to be the cross talk between serotonin and endocannabinoid receptors within the body. According to a study from 2015, CB1 and 5-HT2A receptors can weave together and function as a combined entity. The endogenous (meaning produced within the body) cannabinoid anandamide demonstrates 5-HT1A activity. In contrast, CBD is a “modest affinity agonist” at the human 5-HT1A receptor and may bind receptor type 2 at higher concentrations.  An antagonist is a substance that increases the activity of a receptor when binding to it. Interestingly, CBDA, the acid version of CBD found in the raw plant, is a stronger agonist of 5-HT1A (the other serotonin receptor) than CBD itself. CBDA is also known to be non-psychoactive, as it doesn’t bind to CB1 receptors. 
You don’t trip on CBD, but it is psychotropic by virtue of its anxiolytic (anti-anxiety) and antipsychotic effects. Further research needs to be done to discern the particular influence CBD has on serotonin receptors and why it doesn’t produce the same effect as psychedelic drugs on those receptor sites. It could be that CBD might be an antagonist rather than an agonist. 
Our friend THC, widely known as the “high causer” of the cannabis plant, is simultaneously revered and stigmatized. THC can be defined as hallucinogenic. In high doses, it can produce changes in perception, visual hallucinations, and overall shifts in consciousness, thoughts, and emotions. This is because THC directly activates the CB1 cannabinoid receptor. THC can be hallucinogenic, but not psychedelic, because it does not bind directly to 5-HT2A. CBD has been found to mitigate some of the temporary unfavorable effects of THC’s CB1 binding affinity, such as producing paranoia, shortness of breath, and a rapid heart rate. 
Cannabis terpenes (a la the “riot of perfumes” described by aforementioned Rimbaud) play a vital role in the varied effects of different chemovars (erroneously referred to as “strains”). That’s why a particular chemovar of cannabis with the same percentage of THC can get someone very high, while another doesn’t demonstrate the same effects. Certain terpenes may also help to buffer THC’s psychoactivity. For example, limonene reduces anxiety which may be helpful when someone has taken too much THC, and pinene may be able to reduce the impact of THC’s short-term memory impairment. 
Ketamine, a recreational club drug and an anesthesia used in veterinary and human medicine, binds to CB1 receptors. It’s action on CB1 is how it produces pain-relieving properties.  Ketamine is not technically a psychedelic, but definitely causes a high. Examining these worlds demonstrates that it is not one receptor or compound that is causing a particular effect. It is a combination of factors.
There are a multitude of ways that cannabis can affect consciousness. The plant cannot be reduced down to mere components. The Entourage Effect tells us that the symphony of its chemical constituents are greater together than they are apart. Some chemovars of cannabis are psychoactive, and that’s not a bad thing. Most are not psychedelic. And that’s also incredibly useful.
There’s a complex relationship between substances and human understanding. We can decide for ourselves what’s in a name, and continue to learn more about this incredible plant, perhaps never having the opportunity to figure it out entirely. Now that’s trippy!