pre·cip·i·tant 
(prĭ-sĭpĭ-tənt)
(prĭ-sĭpĭ-tənt)adj.
1. Rushing or falling headlong.
2. Acting with or marked by impulsiveness in thought or action; rash. See Usage Note at precipitate.
3. Abrupt or unexpected; sudden.
n.
Chemistry
Chemistry
A substance that causes a precipitate to form when it is added to a solution.
[Latin praecipitāns, praecipitant-, present participle of praecipitāre, to throw headlong; see PRECIPITATE.]
pre·cipi·tant·ly adv.