noun.
The quality of being buoyant, that is, of floating in or on the surface of water or other fluids; relative lightness.
noun.
The power of supporting a body so that it floats: said of a fluid; specifically, the upward pressure exerted upon a body by the fluid in which it is immersed.
noun.
Figuratively, light-heartedness; cheerfulness; hopefulness; elasticity of spirit.