A local widening and bulging of a blood vessel (an aneurysm) within the thorax (chest). See: Aortic aneurysm. An aneurysm is a localized widening (dilatation) of an artery, the aorta . 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&q [..]