Buoyancy

n. floatability; lightness, cheerfulness, joyfulness

In physics, buoyancy is the upward force on an object produced by the surrounding fluid (i.e., a liquid or a gas) in which it is fully, or partially immersed, due to the pressure difference of the fluid between the top and bottom of the object. The net upward buoyancy force is equal to the magnitude of the weight of fluid displaced by the body. This force enables the object to float or at least to seem lighter. Buoyancy is important for many vehicles such as boats, ships, balloons, and airships.
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Noun
1. cheerfulness that bubbles to the surface
(synonym) perkiness
(hypernym) cheerfulness, blitheness
2. the property of something weightless and insubstantial
(synonym) airiness
(hypernym) lightness, weightlessness
3. irrepressible liveliness and good spirit; "I admired his bouyancy and persistent good humor"
(synonym) irrepressibility
(hypernym) liveliness, life, spirit, sprightliness

(n.)
The upward pressure exerted upon a floating body by a fluid, which is equal to the weight of the body; hence, also, the weight of a floating body, as measured by the volume of fluid displaced.
  

(n.)
The property of floating on the surface of a liquid, or in a fluid, as in the atmosphere; specific lightness, which is inversely as the weight compared with that of an equal volume of water.
  

(n.)
Cheerfulness; vivacity; liveliness; sprightliness; -- the opposite of heaviness; as, buoyancy of spirits.
  

n.
1.
اُتھلائي , ہلکا پن
2. (of spirits)
زندہ دلي , خوش طبعي