Aneurysm, berry: A berry aneurysm is a small outpouching (aneurysm) that looks like a berry and classically occurs at the point at which a cerebral artery departs from the circular artery (the circle of Willis) at the base of the brain. Berry aneurysms often rupture and bleed. Also called a brain aneurysm.

An aneurysm is a localized dilatation (widening) of a blood vessel (an artery or a vein) or the heart. At the area of the aneurysm, the wall is weakened, bulging, and at risk of rupture (breaking).

The word "aneurysm" comes from the Greek "aneurysma" meaning "a widening."