simple past tense and past participle of improvize

(transitive) To make (something) better; to increase the value or productivity (of something). / (intransitive) To become better. / (obsolete) To disprove or make void; to refute.

The act of improving; advancement or growth; a bettering

plural of improvement

To perform improv.

(informal) Improvisation. / (acting) A form of live entertainment characterized by improvisation and interaction with the audience.

present participle of improve

That tends to improve someone or something (especially (dated) to educate or morally better a person).

Capable of being improved. / Capable of being used to advantage; profitable.

Impossible to prove.