[blad.der] n [ME, fr. OE blaedre; akin to OHG blatara bladder, OE blawan to blow] (bef. 12c) 1 a: a membranous sac in animals that serves as the receptacle of a liquid or contains gas; esp: urinary bladder b: cyst 2b
2: something (as the rubber bag inside a football) resembling a bladder -- blad.der.like adj