'Depressant' definitions:

Definition of 'depressant'

From: WordNet
adjective
Capable of depressing physiological or psychological activity or response by a chemical agent [ant: stimulative]
noun
A drug that reduces excitability and calms a person [syn: sedative, sedative drug, depressant, downer]

Definition of 'Depressant'

From: GCIDE
  • Depressant \De*press"ant\, n. (Med.) An agent or remedy which lowers the vital powers. [1913 Webster]