The Collaborative International Dictionary of English v.0.48:

Rehash \Re*hash"\ (r?*h?sh"), v. t.
   To hash over again; to prepare or use again; as, to rehash
   old arguments.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Rehash \Re*hash"\, n.
   Something hashed over, or made up from old materials.
   [1913 Webster]

WordNet (r) 3.0 (2006):

rehash
    n 1: old material that is slightly reworked and used again;
         "merely a dull rehash of his first novel"
    v 1: present or use over, with no or few changes
    2: go back over; "retrograde arguments" [syn: retrograde,
       rehash, hash over]

Moby Thesaurus II by Grady Ward, 1.0:

59 Moby Thesaurus words for "rehash":
   battologize, copy, critique, dwelling upon, elaboration, fill,
   give an encore, go over, go through, going over, iterate,
   iteration, pad, paraphrase, practice, practicing, reaffirm,
   reaffirmation, rearrange, rearrangement, reassert, recap,
   recapitulate, recapitulation, recital, recite, recount, recountal,
   recounting, redo, redoing, rehearsal, rehearse, reissue, reiterate,
   reiteration, rephrase, reprint, reshuffle, reshuffling, restate,
   restatement, resume, retail, retell, retelling, reuse, review,
   reword, rewording, rework, run over, say over, say over again,
   sum up, summarize, summary, summing up, tautologize