brittle
capricious
changeable
corruptible
deciduous
dying
ephemeral
evanescent
fading
fickle
fleeting
flitting
fly-by-night
flying
fragile
frail
fugacious
fugitive
impermanent
impetuous
impulsive
inconstant
insubstantial
momentary
mortal
mutable
nondurable
nonpermanent
passing
perishable
short-lived
temporal
temporary
transient
transitive
transitory
unenduring
unstable
volatile