v.
 (ad-libs, ad-libbing, ad-libbed)
 speak or perform in public without preparing in advance.
adv.
 & 
adj.
   - spoken without advance preparation.
 - Music  with free rhythm and expression.
 - as much and as often as desired.
 
n.
 an ad-lib remark or speech.
 
  Etymology
  C19: abbrev. of ad libitum.