The Collaborative International Dictionary of English v.0.48:

Postpone \Post*pone"\, v. t. [imp. & p. p. Postponed; p. pr. &
   vb. n. Postponing.] [L. postponere, postpositum; post after
   + ponere to place, put. See Post-, and Position.]
   1. To defer to a future or later time; to put off; also, to
      cause to be deferred or put off; to delay; to adjourn; as,
      to postpone the consideration of a bill to the following
      day, or indefinitely.
      [1913 Webster]

            His praise postponed, and never to be paid.
                                                  --Cowper.
      [1913 Webster]

   2. To place after, behind, or below something, in respect to
      precedence, preference, value, or importance.
      [1913 Webster]

            All other considerations should give way and be
            postponed to this.                    --Locke.
      [1913 Webster]

   Syn: To adjourn; defer; delay; procrastinate.
        [1913 Webster]

WordNet (r) 3.0 (2006):

postpone
    v 1: hold back to a later time; "let's postpone the exam" [syn:
         postpone, prorogue, hold over, put over, table,
         shelve, set back, defer, remit, put off]

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "postpone":
   adjourn, continue, dally, defer, delay, drag out, extend,
   hang fire, hang up, hold off, hold over, hold up, lay aside,
   lay away, lay by, lay over, pigeonhole, prolong, prorogate,
   prorogue, protract, push aside, put aside, put away,
   put in mothballs, put off, put on ice, recess, reserve, set aside,
   set by, shelve, shift off, sideline, sleep on, stand over,
   stave off, stay, store, stow, stretch out, suspend, table,
   table the motion, take a recess, temporize, waive