An aneurysm is a bulge in the weakened wall of an artery, most often the aorta. It is similar to what one would see when there is a bubble in the wall of a garden hose. If an aneurysm becomes large enough, it can burst, resulting in a stroke if it is in a brain artery or massive hemorrhage if it is the wall of the aorta. If an aneurysm bursts, the massive bleeding is often fatal.