Here is another word, still from the first chapter of The Great Gatsby. Don't you all feel super intellectual?
To improvise, whether it be with speech, music or just general life.
Sentence example: Annie felt she had to extemporise in her audition as she had forgotten to learn her monologue.
*DISCLAIMER: We at T.E.R. do not recommend following Annie's example. It's scary and makes you shake a lot.*