ad lib vs off the top of head

ad lib

adv

  • Extemporaneously. 

  • At will. 

  • To whatever extent. 

  • At pleasure. 

verb

  • To perform without preparation. 

  • To perform without script. 

  • To perform extemporaneously. 

adj

  • Extemporaneous, impromptu. 

off the top of head

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