1. The amassment of blood between the dura mater, or hard matter; and the arachnoid, the middle of the three layers of the meninges or the thin, delicate, intermediate membranes covering the brain and the spinal cord: A durematoma forms when blood escapes from the vessels and collects as a clot rather than being a growth of cells or a tumor.

2. Etymology: from Latin dura, feminine of durus, "hard" + Greek haima, "blood" + oma,"tumor".