Source : Webster's Revised Unabridged Dictionary (1913)

Unwell \Un*well"\, a.
   1. Not well; indisposed; not in good health; somewhat ill;
      ailing.

   2. (Med.) Specifically, ill from menstruation; affected with,
      or having, catamenial; menstruant.

   Note: This word was formerly regarded as an Americanism, but
         is now in common use among all who speak the English
         language.

Source : WordNet®

unwell
     adj 1: undergoing menstruation [syn: {menstruating}]
     2: somewhat ill or prone to illness; "my poor ailing
        grandmother"; "feeling a bit indisposed today"; "you look
        a little peaked"; "feeling poorly"; "a sickly child"; "is
        unwell and can't come to work" [syn: {ailing}, {indisposed},
         {peaked(p)}, {poorly(p)}, {sickly}, {under the weather}]