something that calms the brain.

One who or that which tranquillizes; spec. any of a large class of drugs in widespread use since the 1950s for the reduction of tension or…

A substance that quiets or soothes; a sedative or narcotic drug (cf. quieter, n., quietant, n.). Also in extended use.

A medical agent which quiets inordinate action of an organ; transferred and figurative anything which has a calming effect.

A drug used as a sedative or muscle relaxant.

Medicine. Of drugs: inducing calmness, tranquillizing. Hence as n., a drug of this kind.

A neuroleptic drug; an antipsychotic drug.

slang. A depressant or tranquillizing drug, especially a barbiturate. Cf. upper, n.2 1, down, n.4 1d.

= tranquillizer, n.