Entry 1 sense Webster, 1913 Menstruation /mĕnˌ-stro͞o-āsh'-ən/ · Men·stru·a·tion · IPA /ˌmɛnstɹuˈeɪʃən/ 01 n. The discharge of the menses; also, the state or the period of menstruating. 1. The discharge of the menses; also, the state or the period of menstruating.