Aneurysm, fusiform: An aneurysm is a localized widening (dilatation) of an artery, vein, or the heart. At the area of an aneurysm, there is typically a bulge and the wall is weakened and may rupture. The word "aneurysm" comes from the Greek "aneurysma" meaning "a widening." A fusiform aneurysm is shaped like a spindle. A fusiform widening of an artery or vein. The word "fusiform" comes from the Latin "fusus" meaning "spindle."