Source : Webster's Revised Unabridged Dictionary (1913)

Buoyant \Buoy"ant\, a. [From {Buoy}, v. t. & i.]
   1. Having the quality of rising or floating in a fluid;
      tending to rise or float; as, iron is buoyant in mercury.
      ``Buoyant on the flood.'' --Pope.

   2. Bearing up, as a fluid; sustaining another body by being
      specifically heavier.

            The water under me was buoyant.       --Dryden.

   3. Light-hearted; vivacious; cheerful; as, a buoyant
      disposition; buoyant spirits. -- {Buoy"ant*ly}, adv.

Source : WordNet®

buoyant
     adj 1: tending to float on a liquid or rise in air or gas; "buoyant
            balloons"; "buoyant balsawood boats"; "a floaty scarf"
            [syn: {floaty}]
     2: characterized by liveliness and light-heartedness; "buoyant
        spirits"; "his quick wit and chirpy humor"; "looking
        bright and well and chirpy"; "a perky little widow in her
        70s" [syn: {chirpy}, {perky}]