Source : Webster's Revised Unabridged Dictionary (1913)

Effervescence \Ef`fer*ves"cence\, Effervescency
\Ef`fer*ves"cen*cy\, n. [Cf. F. effervescence.]
   A kind of natural ebullition; that commotion of a fluid which
   takes place when some part of the mass flies off in a gaseous
   form, producing innumerable small bubbles; as, the
   effervescence of a carbonate with citric acid.

Source : WordNet®

effervescence
     n 1: the process of bubbling as gas escapes
     2: the property of giving off bubbles [syn: {bubbliness}, {frothiness}]