buoy·ant /ˈbɔɪənt, ˈbujənt/
  (a.)有浮力的,心情愉快的
  Buoy·ant a.
  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.”
  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.
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  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]