Noun

• S: (n) sedative, sedative drug, depressant, downer (a drug that reduces excitability and calms a person)

Adjective

• S: (adj) ataractic, ataraxic, sedative, tranquilizing, tranquillizing, tranquilising, tranquillising (tending to soothe or tranquilize) "valium has a tranquilizing effect"; "took a hot drink with sedative properties before going to bed"