ephemeral

transient, transitory, ephemeral, momentary, fugitive, fleeting, evanescent mean lasting or staying only a short time. transient applies to what is actually short in its duration or stay.

• • a hotel catering primarily to transient guests

transitory applies to what is by its nature or essence bound to change, pass, or come to an end.

• • fame in the movies is transitory

ephemeral implies striking brevity of life or duration.

• • many slang words are ephemeral

momentary suggests coming and going quickly and therefore being merely a brief interruption of a more enduring state.

• • my feelings of guilt were only momentary

fugitive and fleeting imply passing so quickly as to make apprehending difficult.

• • let a fugitive smile flit across his face
• • fleeting moments of joy

evanescent suggests a quick vanishing and an airy or fragile quality.

• • the story has an evanescent touch of whimsy that is lost in translation