Precipitate

[Sarah]

An insoluble substance separated from a solution in a concretestate by the action of some reagent added to the solution, or of someforce, such as heat or cold. The precipitate may fall to the bottom(whence the name), may be diffused through the solution, or may floatat or near the surface. Red precipitate (Old. Chem), mercuric oxide(HgO) a heavy red crystalline powder obtained by heating mercuricnitrate, or by heating mercury in the air. Prepared in the lattermanner, it was the precipitate per se of the alchemists.-- White precipitate (Old Chem.) (a) A heavy white amorphous powder(NH2.HgCl) obtained by adding ammonia to a solution of mercuricchloride or corrosive sublimate; -- formerly called also infusiblewhite precipitate, and now amido-mercuric chloride. (b) A whitecrystalline substance obtained by adding a solution of corrosivesublimate to a solution of sal ammoniac (ammonium chloride); --formerly called also fusible white precipitate.

[Sarah]

to happen suddenly or unexpectedly ; done or acting without careful thought and consideration.

[Sarah]

To rain...(it can rain a number of things, but please see the example for proper usage).

[Luis Fok]

to make something happen suddenly or sooner than expected:

[Couch Potatoe]

Cause (an event or situation, typically one that is bad or undesirable) to happen suddenly, unexpectedly, or prematurely.