1. (v. t.) To compose, recite, or sing extemporaneously\, especially in verse; to extemporize; also, to play upon an instrument, or to act, extemporaneously.

2. (v. t.) To bring about, arrange, or make, on a sudden, or without previous preparation.

3. (v. t.) To invent, or provide, offhand, or on the spur of the moment; as, he improvised a hammer out of a stone.

4. (v. i.) To produce or render extemporaneous compositions, especially in verse or in music, without previous preparation; hence, to do anything offhand.

ad lib ad-lib be caught napping be surprised be taken unawares be unprepared beget breed bring forth bring into being call into being coin conceive concoct contrive cook up dash off design develop devise discover do offhand dream up engender evolve extemporize fabricate fake frame generate give being to give rise to go off half-cocked hatch have no plan improvisate invent jury-rig knock off lash up make do make do with make up mature mint originate plan play by ear procreate scrap the plan spawn strike off strike out think out think up throw off throw together toss off toss out vamp whip up whomp up wing it