Source : Webster's Revised Unabridged Dictionary (1913)

Dichotomous \Di*chot"o*mous\, a. [L. dichotomos, Gr. ?; ? in
   two, asunder + diate`mnein to cut.]
   Regularly dividing by pairs from bottom to top; as, a
   dichotomous stem. -- {Di*chot"o*mous*ly}, adv.

Source : WordNet®

dichotomous
     adj : divided or dividing into two sharply distinguished parts or
           classifications