ad lib vs busk it

ad lib

verb

  • To perform without preparation. 

  • To perform without script. 

  • To perform extemporaneously. 

adv

  • Extemporaneously. 

  • At will. 

  • To whatever extent. 

  • At pleasure. 

adj

  • Extemporaneous, impromptu. 

busk it

How often have the words ad lib and busk it occurred in a corpus of books? (source: Google Ngram Viewer )