Source : Webster's Revised Unabridged Dictionary (1913)

Twain \Twain\, a. & n. [OE. twein, tweien, tweyne, AS.
   tw[=e]gen, masc. See {Two}.]
   Two; -- nearly obsolete in common discourse, but used in
   poetry and burlesque. ``Children twain.'' --Chaucer.

         And whosoever shall compel thee to go a mile, go with
         him twain.                               --Matt. v. 41.

   {In twain}, in halves; into two parts; asunder.

            When old winder split the rocks in twain. --Dryden.

   {Twain cloud}. (Meteor.) Same as {Cumulo-stratus}.