1) Involving or causing delirium 
Deliriants are a class of hallucinogen. The term was introduced by David F. Duncan and Robert S. Gold to distinguish these drugs from psychedelics and dissociatives, such as LSD and ketamine respectively, due to their primary effect of causing delirium, as opposed to the more lucid states produced by other hallucinogens (psychedelics and dissociat...
• (n.) A poison which occasions a persistent delirium, or mental aberration (as belladonna).
De·lir'i·ant noun [ See Delirium .] (Medicine) A poison which occasions a persistent delirium, or mental aberration (as belladonna). 
deliriant 1. A poison which occasions a persistent delirium, or mental aberration; such as, belladonna. 2. Capable of producing delirium. 3. A drug which may produce delirium. 4. A delirious person.
involving or causing delirium.