a bag or sac in animals, which serves as the receptacle of some fluid; as, the urinary bladder; the gall bladder; -- applied especially to the urinary bladder, either within the animal, or when taken out and inflated with air.-any vesicle or blister, especially if filled with air, or a thin, watery fluid.-a distended, membranaceous pericarp.-anything inflated, empty, or unsound.-to swell out like a bladder with air; to inflate.-to put up in bladders; as, bladdered lard.