ad-lib /ˌæd ˈlɪb/ BrE AmE verb ( past tense and past participle ad-libbed , present participle ad-libbing )
[ Date: 1900-2000 ; Origin: ad lib 'without any preparation' (19-21 centuries) , from Modern Latin ad libitum 'according to desire' ]
[intransitive and transitive] to say things that you have not prepared or planned when you are performing or giving a speech SYN improvise :
I never use a script; I just ad lib the whole programme.
—ad-lib noun [countable]