Synonyms for Transient (same or very similar meaning)
WordNet sense 1 (lasting a very short time):
ephemeral, passing, short-lived, transitory, fugacious
WordNet sense 2 (not permanent; not lasting):
impermanent, temporary
WordNet sense 3 (of a mental act; causing effects outside the mind):
transeunt
From the ODE community, based on WordNet
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