Source : Webster's Revised Unabridged Dictionary (1913)

Expatiate \Ex*pa"ti*ate\, v. i. [imp. & p. p. {Expatiated}; p.
   pr. & vb. n. {Expariating}.] [L. expatiatus, exspatiatus, p.
   p. of expatiari, exspatiari, to expatiate; ex out + spatiari
   to walk about spread out, fr. spatium space. See {Space}.]
   1. To range at large, or without restraint.

            Bids his free soul expatiate in the skies. --Pope.

   2. To enlarge in discourse or writing; to be copious in
      argument or discussion; to descant.

            He expatiated on the inconveniences of trade.
                                                  --Addison.

Expatiate \Ex*pa"ti*ate\, v. t.
   To expand; to spread; to extend; to diffuse; to broaden.

         Afford art an ample field in which to expatiate itself.
                                                  --Dryden.

Source : WordNet®

expatiate
     v : add details, as to an account or idea; clarify the meaning
         of and discourse in a learned way, usually in writing;
         "She elaborated on the main ideas in her dissertation"
         [syn: {elaborate}, {lucubrate}, {exposit}, {enlarge}, {flesh
         out}, {expand}, {expound}, {dilate}] [ant: {abridge}]