[ad-lib, ad-]

verb (used with object), ad-libbed, ad-lib·bing.

to improvise all or part of (a speech, a piece of music, etc.): to ad-lib one's lines.

verb (used without object), ad-libbed, ad-lib·bing.

to act, speak, etc., without preparation: Throughout the play he had to ad-lib constantly.


impromptu; extemporaneous: ad-lib remarks to hecklers.

Origin of ad-lib

1915–20, Americanism; v. use of ad lib
Related formsad-lib·ber, noun

ad lib

[ad lib, ad]


something improvised in speech, music, etc.: Was that joke part of your speech or an ad lib?


at one's pleasure; without restriction.
freely; as needed; without stint: Water can be given to the patients ad lib.

Origin of ad lib

First recorded in 1810–20; see origin at ad libitum

ad lib. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for ad-lib

Contemporary Examples of ad-lib

British Dictionary definitions for ad-lib


verb -libs, -libbing or -libbed

to improvise and deliver without preparation (a speech, musical performance, etc)

adjective (ad lib when predicative)

improvised; impromptu

adverb ad lib

without restraint; freely
music short for ad libitum


an improvised performance, often humorous
Derived Formsad-libber, noun

Word Origin for ad-lib

C18: short for Latin ad libitum, literally: according to pleasure
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for ad-lib

ad lib

1811, shortened from Latin ad libitum "at one's pleasure, as much as one likes" (c.1600), from libere "to please" (see libido). First recorded as one word 1919 (v.), 1925 (n.).

Online Etymology Dictionary, © 2010 Douglas Harper

ad-lib in Medicine

ad lib.


ad libitum (freely, as desired)
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.