Precipitate usually means "bringing something on" or "making it happen" — and not always in a good way. An unpopular verdict might "precipitate violence" or one false step at the Grand Canyon could precipitate you down into the gorge.
Precipitate, as a verb, can also mean specifically, "to fall from clouds," such as rain, snow, or other forms of precipitation. When used as an adjective, precipitate means "hasty" or "acting suddenly." If you decide to throw your class project in a trash masher just because someone in your class had a similar idea, then your actions might be described as precipitate. Or if you do that sort of thing regularly, you may be a precipitate person.