a bleb; a vesicle, or an elevation of the cuticle, containing a transparent watery fluid.-the ovoid prominence below the opening of the ear in the skulls of many animals; as, the tympanic or auditory bulla.-a leaden seal for a document; esp. the round leaden seal attached to the papal bulls, which has on one side a representation of st. peter and st. paul, and on the other the name of the pope who uses it.-a genus of marine shells. see bubble shell.