Buoy'an-cy, n.

(bwōy'-, or bwŏy'-), n. [From buoyant.]

1. The quality of floating on the surface of a fluid, or in the atmosphere; specific lightness, which is inversely as the weight compared with that of an equal volume of water.
2. (Physics.) The weight of a floating body, as measured by the volume of fluid displaced.

Such are the buoyances or displacements of the different classes of her majesty's ships. Eng. Cyc. 3. Cheerfulness; vivacity; as, buoyancy of spirits.