• A balloon type pouch or bulge in the wall of a cerebral blood vessel.
  NCI
  U.S. National Cancer Institute, 2021
• A weakening and ballooning of the wall of an artery in the brain.
  Harvard Dictionary of Health Terms
  Harvard Medical Publishing, 2011
• Congenital or acquired abnormal outpouching of an intracranial blood vessel wall; saccular (berry) aneurysms are the most common variant, and tend to form at arterial branch points near the base of the brain; rupture results in subarachnoid hemorrhage or intracranial hemorrhages; giant aneurysms (>2.5 cm in diameter) may compress adjacent structures, including the oculomotor nerve.
  CRISP Thesaurus
  National Institutes of Health, 2006
• A consequence of cerebral aneurysm, aneurysmal subarachnoid hemorrhage (SAH) has devastating consequences. About 10% of individuals with aneurysmal SAH die before reaching medical attention, 25% die within 24 hours, and 40-49% die within 3 months.
  Medscape
  WebMD, 2025
• A cerebral aneurysm is an acquired focal abnormal dilation of the wall of an artery in the brain. Intracranial aneurysms are most commonly located at branching points of the major arteries at the base of the brain, which course through the subarachnoid space. Cerebral aneurysms can, by nature of their size, compress neighboring nerves or...
  Epocrates
  Athenahealth, Inc., 2019