subject to change or variation especially in behavior; "her unsteady walk"; "his hand was unsteady as he poured the wine"; "an unsteady voice"
10
fleeting
lasting for a markedly brief time; "a fleeting glance"; "fugitive hours"; "rapid momentaneous association of things that meet and pass"; "a momentary glimpse"
1
agile
moving quickly and lightly; "sleek and agile as a gymnast"; "as nimble as a deer"; "nimble fingers"; "quick of foot"; "the old dog was so spry it was halfway up the stairs before we could stop it"