[ad-lib, ad-]
verb (used with object), ad-libbed, ad-lib·bing.
  1. 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.
  1. to act, speak, etc., without preparation: Throughout the play he had to ad-lib constantly.
  1. impromptu; extemporaneous: ad-lib remarks to hecklers.

Origin of ad-lib

1915–20, Americanism; v. use of ad lib
Related formsad-lib·ber, noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for adlibbing


verb -libs, -libbing or -libbed
  1. to improvise and deliver without preparation (a speech, musical performance, etc)
adjective (ad lib when predicative)
  1. improvised; impromptu
adverb ad lib
  1. without restraint; freely
  2. music short for ad libitum
  1. 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