1Lasting only a moment; momentary (Linguistics, with reference to the time taken to perform the action expressed by a verb).
historical Designating the increment in the value of a time-varying quantity that occurs in an infinitesimal period of time. Compare "moment", "momentary".
Late Middle English; earliest use found in John Lydgate (c1370–c1449), poet and prior of Hatfield Regis. From post-classical Latin momentaneus momentary (Vetus Latina), instantaneous + -ous.