WordNet (r) 3.0 (2006):

work on
    v 1: to exert effort in order to do, make, or perform something;
         "the child worked at the multiplication table until she had
         it down cold" [syn: work at, work on]
    2: shape, form, or improve a material; "work stone into tools";
       "process iron"; "work the metal" [syn: work, work on,
       process]

Moby Thesaurus II by Grady Ward, 1.0:

87 Moby Thesaurus words for "work on":
   abuse, act on, act upon, advocate, affect, apply pressure,
   approach, bear upon, beset, besiege, blandish, bleed, bleed white,
   bug, buttonhole, cajole, call on, call upon, coax, concentrate on,
   deceive, drain, draw, draw on, dun, exert influence,
   exert pressure, exhort, exploit, focus on, foist on, get cozy with,
   high-pressure, ill-use, importune, impose on, impose upon,
   influence, insist, insist upon, jawbone, lead on, lobby,
   lobby through, magnetize, make advances, make overtures,
   make up to, make use of, manipulate, milk, misuse, nag, nag at,
   operate on, pass off on, pass the buck, pester, plague, play on,
   plead with, ply, press, pressure, presume upon, pull strings, push,
   put across, put on, put over, put upon, recommend, shift the blame,
   shift the responsibility, soft-soap, stroke, suck dry, sweet-talk,
   take advantage of, tease, treat, urge, use, use ill, wheedle,
   wire-pull, work upon