1) A relatively common neoplasm of the central nervous system that arises from arachnoidal cells. The majority are well differentiated vascular tumors which grow slowly and have a low potential to be invasive, although malignant subtypes occur. Meningiomas have a predilection to arise from the parasagittal region, cerebral convexity, sphenoidal ridge, olfactory groove, and spinal canal. They tend to present in the fourth to sixth decades of life with signs indicative of a slowly progressive mass lesion. Specific clinical manifestations depend on the location of the tumor, but may include intracranial hypertension, cranial neuropathies, ataxia, and other focal neurologic signs. (From DeVita et al., Cancer: Principles and Practice of Oncology, 5th ed, pp2056-7)

2) A slow-growing encapsulated tumor arising from the meninges and often causing damage by pressing upon the brain and adjacent parts.

3) A type of tumor that occurs in the meninges, the membranes that cover and protect the brain and spinal cord. Meningiomas usually grow slowly.