evanescent

adjective6

1. •
   Disappearing, vanishing.

   • The sea was each little bird's great playmate. […] In their airy flutterings, they seemed to rest on the evanescent spray. — 1842
2. •
   Ephemeral, fleeting, momentary.

   • It is to be observed, farther, that when we annihilate any thing in our Mind, we consider it as something evanescent, and removed out of Sight; […] — 1732
3. •
   Of plant parts: shed after a period.

   • Per[ianth]. Berry from the receptacle elongated into a cup globular, succulent, gaging at the top, colour'd, at length wasting from dryness, evanescent. — 1787
4. •
   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.
5. •
   Of a number or value: diminishing to the point of reaching zero as a limit; infinitesimal.

   • Some hold the evanescent increments to be real quantities, some to be nothings, some to be limits. As many Men, so many minds: Each differing one from another, and all from Sir Isaac Newton. — 1735
6. •
   Barely there; almost imperceptible.

   • If the Fluids moving in an Evanescent Artery [i.e., a capillary] appear Globular, I suppose its because the Canal is round, which alters the Case much. — 1709