ad–lib 
/ˈædˈlɪb/ verb
ad–libs; ad–libbed; ad–lib·bing /ˈædˈlɪb/ verb : to make up words or music in a performance instead of saying or playing something that has been planned : improvise [no obj] ▪ The actor forgot his lines, so he ad-libbed. ▪ a comedian who is admired for his ability to ad-lib [+ obj] ▪ The actor ad-libbed his lines. ▪ She ad-libbed the guitar solo. ▪ ad-lib a joke
— ad–lib noun, plural ad–libs [count]
▪ Some of the best jokes in the movie were ad-libs.
▪ Some of the best jokes in the movie were ad-libs.
— ad–lib adjective
▪ an ad-lib joke
▪ an ad-lib joke
— ad–lib adverb
▪ did the whole dialogue ad-lib
▪ did the whole dialogue ad-lib
