adjective

lasting for a very short time.

for a fleeting moment I saw the face of a boy

brief,transient,short-lived,short,momentary,sudden,cursory,transitory,ephemeral,fugitive,evanescent,fading,vanishing,flying,fly-by-night,passing,flitting,here today and gone tomorrow,temporary,impermanent,short-term,rapid,quick,swift,rushed,fugacious