/men"strooh euhl, -streuhl/ , adj.
1. of or pertaining to menstruation or to the menses.
2. Archaic. monthly.
[ 1350-1400; ME menstruall menstrualis having monthly courses, equiv. to menstru ( a ) monthly courses (n. use of neut. pl. of MENSTRUUS monthly; menstr- (see SEMESTER) + -uus adj. suffix, prob. on the model of annuus ANNUAL) + -alis -AL 1 ]