What does cavernoma or (venous?) vascular malformation mean?

Common and benign: Cavernous malformations, or cavernous angiomas, or cavernomas, are a type of vascular abnormality of the central nervous system. They consist of a cluster of abnormal, dilated vessels. People are typically born with a tendency to have develop them, but are usually benign and most everyone do not have any symptoms, but some may have headaches or neurologic symptoms, and should see a neurologist.