de·pres·sant / diˈpresənt/ • adj. (chiefly of a drug) reducing functional or nervous activity.• n. a depressant drug. ∎  an influence that depresses economic or other activity: higher taxation is a depressant.

depressant (di-pres-ănt) n. an agent that reduces the normal activity of any body system or function. Drugs such as general anaesthetics, barbiturates, and opioids are depressants of the central nervous system and respiration.