WordNet (r) 3.0 (2006):

rub out
    v 1: remove by or as if by rubbing or erasing; "Please erase the
         formula on the blackboard--it is wrong!" [syn: erase,
         rub out, score out, efface, wipe off]

Moby Thesaurus II by Grady Ward, 1.0:

90 Moby Thesaurus words for "rub out":
   abbreviate, ablate, abrade, abrase, abridge, annihilate,
   assassinate, bark, blast, blot, blot out, blue-pencil, bowdlerize,
   bump off, cancel, censor, chafe, cool, croak, cross out, cut,
   decimate, dele, delete, demolish, do in, dust off, edit, edit out,
   efface, erase, erode, expunge, expurgate, file, finish, fix, fray,
   frazzle, fret, gall, get, give the business, gnaw, gnaw away,
   grate, graze, grind, gun down, hit, ice, kill, knock off, lay out,
   liquidate, obliterate, off, omit, polish off, put away, rasp, raze,
   rescind, rub away, rub off, ruin, rule out, scour, scrape, scratch,
   scratch out, scrub, scuff, settle, shatter, skin, smash, sponge,
   sponge out, strike, strike off, strike out, take care of, void,
   waste, wear, wear away, wipe out, wreck, zap