Something which causes or hastens the occurrence of an act or event; specifically (chiefly psychology), something which brings about a mental or physiological condition.

(chemistry) A substance that, when added to a solution, causes a dissolved substance to form a precipitate.

Inclined to make rapid decisions without due consideration; hasty, impulsive, rash.

Of a fall: straight downwards; headlong.

(chiefly figurative) Acting, happening, or moving quickly; fast, rapid, swift; also, abrupt, sudden, unexpected.

(chemistry) That causes precipitation (“formation of a heavier solid in a lighter liquid as a result of a chemical reaction”).

(archaic) Synonym of precipitantly (“in a precipitant or headlong manner; with foolish or rash haste”)