1. An aneurysm that is a localized widening (dilatation) of an artery, vein, or of the heart: A racemose aneurysm looks like a bunch of grapes.

At the area of an aneurysm, there is typically a bulge, called a racemose aneurysm, and the wall is weakened and may rupture.
2. Etymology: originally "aneurysm" comes from the Greek aneurysma meaning "a widening".