Evanescent

1. Disappearing, vanishing.

Synonym: nonevanescent

• (electromagnetism) Of an oscillating electric or magnetic field: not propagating as an electromagnetic wave but having its energy spatially concentrated in the vicinity of its source.
• (mathematics) Of a number or value: diminishing to the point of reaching zero as a limit; infinitesimal.

2. Barely there; almost imperceptible.
3. Ephemeral, fleeting, momentary.

Synonyms: nonevanescent; ephemeral

• (botany) Of plant parts: shed after a period.