Entry 1 sense Webster, 1913 Subdural · Sub·du·ral · IPA /ˌsʌbˈd(j)ʊɹ.əl/ 01 a. Situated under the dura mater, or between the dura mater and the arachnoid membrane. 1. Situated under the dura mater, or between the dura mater and the arachnoid membrane.(Anat.)