An"eu*rism (&?;), n. [Gr. &?;, &?;, a widening, an opening; &?; up + &?; wide.] (Med.) A soft, pulsating, hollow tumor, containing blood, arising from the preternatural dilation or rupture of the coats of an artery. [Written also aneurysm.]

• (pathology) An abnormal blood-filled swelling of an artery or vein, resulting from a localized weakness in the wall of the vessel.