autoschediasm
/ɔːtə(ʊ)ˈskɛdɪaz(ə)m/noun
That which is autoschediastic; something done on the spur of the moment or without preparation; a hasty improvisation.
Origin
Mid 19th century; earliest use found in Charles Kingsley (1819–1875), novelist, Church of England clergyman, and controversialist. From post-classical Latin autoschediasma or its etymon ancient Greek αὐτοσχεδίασμα work done offhand, improvisation from αὐτοσχεδιάζειν + -μα.