transient

(noun) one who stays for only a short time. Examples: "Transient laborers."

(noun) (physics) a short-lived oscillation in a system caused by a sudden change of voltage or current or load.

(adj) of a mental act; causing effects outside the mind. Synonyms: transeunt (vs. immanent).

(adj) lasting a very short time. Synonyms: ephemeral, passing, short-lived, transitory, fugacious. Examples: "The ephemeral joys of childhood." "A passing fancy." "Youth's transient beauty." "Love is transitory but it is eternal." "Fugacious blossoms."