Buoyant

1. v. t. & i. Light-hearted; vivacious; cheerful; as, a buoyant disposition; buoyant spirits.
2. v. t. & i. Having the quality of rising or floating in a fluid; tending to rise or float; as, iron is buoyant in mercury.
3. v. t. & i. Bearing up, as a fluid; sustaining another body by being specifically heavier.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.