mucocele /myo̅o̅′kōsēl/ [L, mucus, slime; Gk, koilia, cavity] , 1. dilation of a cavity with accumulated mucus secretion. 2. a dome-shaped mucosal swelling caused by a rupture of a salivary gland duct, which spills mucin into the surrounding tissues. A mucocele is usually caused by trauma. See mucus extravasation phenomenon, mucus retention cyst.