"buoyancy" in the noun sense
1. buoyancy, perkiness
cheerfulness that bubbles to the surface
2. airiness, buoyancy
the property of something weightless and insubstantial
3. buoyancy
the tendency to float in water or other liquid
4. irrepressibility, buoyancy
irrepressible liveliness and good spirit
"I admired his buoyancy and persistent good humor"
Source: WordNet® (An amazing lexical database of English)
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