The Collaborative International Dictionary of English v.0.48:

Expound \Ex*pound"\ ([e^]ks*pound"), v. t. [imp. & p. p.
   Expounded; p. pr. & vb. n. Expounding.] [OE. exponen,
   expounen, expounden, fr. L. exponere to set out, expose,
   expound; ex out + ponere to put: cf. OE. expondre, expondre.
   See Position.]
   1. To lay open; to expose to view; to examine. [Obs.]
      [1913 Webster]

            He expounded both his pockets.        --Hudibras.
      [1913 Webster]

   2. To lay open the meaning of; to explain; to clear of
      obscurity; to interpret; as, to expound a text of
      Scripture, a law, a word, a meaning, or a riddle.
      [1913 Webster]

            Expound this matter more fully to me. --Bunyan.
      [1913 Webster]

WordNet (r) 3.0 (2006):

expound
    v 1: 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, expatiate, exposit,
         enlarge, flesh out, expand, expound, dilate]
         [ant: abbreviate, abridge, contract, cut,
         foreshorten, reduce, shorten]
    2: state; "set forth one's reasons" [syn: set forth,
       expound, exposit]

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "expound":
   account for, allegorize, clarify, clear up, comment, construe,
   crack, decipher, delineate, demonstrate, demythologize, describe,
   discourse, elucidate, enlighten, euhemerize, exemplify, explain,
   explain away, explicate, exposit, express, give reason for,
   give the meaning, harangue, hold forth, illuminate, illustrate,
   interpret, lecture, make clear, make plain, moralize,
   point a moral, popularize, preach, present, rationalize,
   read a lesson, sermonize, shed light upon, show, show how,
   show the way, simplify, solve, spell out, state, throw light upon,
   unfold, unlock, unravel