1) Protruding sac in the wall of a vein, artery, or heart, frequently caused by microbial infection; may present as pain, pressure on nearby organs, or cardiac weakening.

2) A sac formed by the dilatation of the wall of an artery, a vein, or the heart.

3) An abnormal blood-filled dilatation of a blood vessel and especially an artery resulting from disease of the vessel wall.