The improper usage of these terminologies has been bugging me, it seems that we are often prone to likening 'psychedelic' and 'hallucinogen' but they aren't the same. Maybe if we get used to terming these substances more accurately, we can more clearly give psychedelic drugs and their creators the respect they deserve.
From top to bottom, here we go:
5HT2a agonists are "psychedelic hallucinogens" (Psychedelics like LSD, Shrooms, 2C-b, DMT...)
Serotonin releasers are "empathogenic-entactogenic hallucinogens" (MDMA, 6-APB, 4-FA, 4-MEC...)
NDMA Antagonists are "dissociative hallucinogens" (DXM, MXE, PCP, Ketamine...)
Less understood hallucinogens are "atypical hallucinogen" (Salvia...)
Then there are "deleriant hallucinogens" (DPH, Jimson Weed, Deadly Nightshade, Amanitas...)
As you can see, 'Hallucinogen' represent a very large and dangerous class of drugs, but 'Psychedelic' represents a very useful and potentially therapeutic class of drugs.