名詞 precipitant:

1. an agent that causes a precipitate to form

形容詞 precipitant:

1. done with very great haste and without due deliberation
   同義詞：hasty, overhasty, precipitate, precipitous

pre.cip.i.tant

adj.（形容詞）
Rushing or falling headlong.
陡斜地沖下或落下的
Acting with or marked by impulsiveness in thought or action; rash.See Usage Note at precipitate
輕率的：在思想或行動(dòng)上操之過急的或特點(diǎn)為沖動(dòng)的；輕率的參見 precipitate
Abrupt or unexpected; sudden.
突如其來的：出其不意的或意外的；突然的
n.Chemistry （名詞）【化學(xué)】
A substance that causes a precipitate to form when it is added to a solution.
沉淀劑：加入溶液中使沉淀物生成的物質(zhì)

來源：
Latin praecipit3ns praecipitant- [present participle of] praecipit3re [to throw headlong] * see precipitate
拉丁語 praecipit3ns praecipitant- [] praecipit3re的現(xiàn)在分詞 [陡斜地拋下] *參見 precipitate

【引伸】
precip.itantly
adv.（副詞）