Webster's Revised Unabridged Dictionary · 1913

Dura mater

Dura mater

[Latin, lit., hard mother. The membrane was called mater, or mother, because it was formerly thought to give rise to every membrane of the body.]

(Anatomy) The tough, fibrous membrane, which lines the cavity of the skull and spinal column, and surrounds the brain and spinal cord; -- frequently abbreviated to dura.