Pronunciation: (ad lib', ad'), [key]
1. something improvised in speech, music, etc.: Was that joke part of your speech or an ad lib?
2. at one's pleasure; without restriction.
3. freely; as needed; without stint: Water can be given to the patients ad lib.
Pronunciation: (ad lib', ad'-), [key]
—v., -libbed, -lib•bing,
to improvise all or part of (a speech, a piece of music, etc.): to ad-lib one's lines.
to act, speak, etc., without preparation: Throughout the play he had to ad-lib constantly.
impromptu; extemporaneous: ad-lib remarks to hecklers.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.