Source : Webster's Revised Unabridged Dictionary (1913)

Menstruate \Men"stru*ate\, v. i. [imp. & p. p. {Menstruated}; p.
   pr. & vb. n. {Menstruating}.]
   To discharge the menses; to have the catamenial flow.

Source : WordNet®

menstruating
     adj : undergoing menstruation [syn: {unwell}]