Antonyms for flabby

baggy, fat:

lean, slim, taut, firm, tight, thin.

noun:

sound, tense, Indurated, rock, sturdy, inelastic, strong, stiff, unbending, fit, resistant, compressed, stiffened, unyielding, condensed, rocklike, case-hardened, adamantine, rigid, substantial, tempered, tough, inflexible, hardened.