Definition of "buoyancy"

buoyancy

/ˈbɔɪ.ən.si/

noun
countable and uncountable, plural buoyancies
1. (physics) The upward force on a body immersed or partly immersed in a fluid.
2. The ability of an object to stay afloat in a fluid.
3. (by extension) Resilience or cheerfulness.
  Quotations
  With how much lighter a step, with how much brighter an eye, did Francesca wander through the forest, even in the last desolation of autumn, than she did in all the bloom and buoyancy of spring!
  1834, L[etitia] E[lizabeth] L[andon], chapter XI, in Francesca Carrara. […], volume III, London: Richard Bentley, […], (successor to Henry Colburn), page 82