without previous preparation

I spoke ad lib

as much and as often as desired

the price includes meals and drinks ad lib

spoken or performed without previous preparation

an ad-lib commentary

occurring, used, or distributed as often as necessary or desired

the pigs are fed on an ad-lib basis

speak or perform in public without previously preparing one's words

Charles had to ad-lib because he'd forgotten his script

a remark or speech made without previous preparation

he came up with an apt ad lib