Source : Webster's Revised Unabridged Dictionary (1913)

Flabby \Flab"by\, a. [See {Flap}.]
   Yielding to the touch, and easily moved or shaken; hanging
   loose by its own weight; wanting firmness; flaccid; as,
   flabby flesh.

Source : WordNet®

flabby
     adj : lacking firmness or stiffness; "flabby around the middle";
           "flaccid cheeks" [syn: {flaccid}]
     [also: {flabbiest}, {flabbier}]