|Origin:||ad lib 'without any preparation' (19-21 centuries), from Modern Latin ad libitum 'according to desire'|
ad-lib past tense and past participle ad-libbed, present participle ad-libbing
[intransitive and transitive]
to say things that you have not prepared or planned when you are performing or giving a speech:
I never use a script; I just ad lib the whole programme.
—ad-lib noun [countable]