The Collaborative International Dictionary of English v.0.48:

Menstruate \Men"stru*ate\, v. i. [imp. & p. p. Menstruated; p.
   pr. & vb. n. Menstruating.]
   To discharge the menses; to have the catamenial flow.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

menstruating \menstruating\ adj.
   discharging menstrual fluid; -- of women during their
   menstrual period.

   Syn: unwell.
        [WordNet 1.5]