impromptu UK /ɪmˈpɹɒmp.tju/US /ɪmˈpɹɑmp.t(j)u/noun 2adjective 1adverb 1verb 1forms 3 noun2 •A short musical composition for an informal occasion often with the character of improvisation and usually to be played solo.The second impromptu is a dance-like Allegretto in A flat major, with a trio in D flat major employing arpeggiated textures. — 1997 •Any composition, musical or otherwise, that is created on the spot without preparation. adjective1 •Improvised; without prior preparation, planning, or rehearsal.The party began with an impromptu rendition of “Happy Birthday”. adverb1 •Extemporaneously; without prior preparation, planning, or rehearsal.was done impromptu verb1 •To compose offhand. formsimpromptued · impromptuing · impromptus