(of trees) losing their leaves annually (especially in autumn)

not around for long

difficult to find, capture etc; not easy to remember

evasive, mysterious

living, lasting, for a very short time

momentary, passing

lasting for a short time

brief, transient

(of) a person running away from the police, danger etc

fleeing, transient

lasting for, done in, a very brief period of time

brief, fleeting

not lasting; the act of going by

brief, casual

(Latin: pro tempore) for the time being

temporary

lasting for, designed to be used for, a limited time only

lasting only a short while

lasting for a short time only

temporary

(of a liquid) that easily changes into gas or vapour; (of a person, mood) changing quickly or easily from one mood or interest to another

explosive, changeable