What is a "lib"?

You may mean “ad lib” - which is a latin short form for ad libitum with literal meaning “ at your pleasure”. In practice it is usually used to refer to a performer (e.g. actor or comedian) who is not sticking rigidly to a script, but is using his or her wits to come up with something original - sometimes to cover up for some unforseen problem like another actor forgetting their lines, or missing an “entrance” or to deal with heckling from the audience. . “Lib.” is also commonly used (especially in the UK) to refer to “Liberal” politics. .

– Best wishes - Majikthise. .