ad-lib

verb (ad-libs, ad-libbing, ad-libbed)

• speak or perform without previously preparing one’s words:Charles had to ad-lib because he’d forgotten his script

adverb & adjective

• 1spoken or performed without previous preparation: [as adjective]:an ad-lib commentary [as adverb]:I spoke ad lib
• Music (especially as a direction) with free rhythm and expression.

• 2as much and as often as desired: [as adverb]:the price includes meals and drinks ad lib

noun

• an ad-lib remark or speech: he came up with an apt ad-lib