WordNet (r) 3.0 (2006):

mop up
    n 1: a concluding action [syn: completion, culmination,
         closing, windup, mop up]
    v 1: to wash or wipe with or as if with a mop; "Mop the hallway
         now"; "He mopped her forehead with a towel" [syn: wipe
         up, mop up, mop]
    2: defeat thoroughly; "He mopped up the floor with his
       opponents" [syn: worst, pip, mop up, whip, rack up]
    3: finish a task completely; "I finally got through this
       homework assignment" [syn: get through, wrap up, finish
       off, mop up, polish off, clear up, finish up]

Moby Thesaurus II by Grady Ward, 1.0:

68 Moby Thesaurus words for "mop up":
   baptize, bath, bathe, beat, button up, cap, carry to completion,
   clean up, climax, clobber, close out, close up, complete, conclude,
   crown, culminate, douche, drub, dust, end, finalize, finish,
   finish off, finish up, flush, flush out, gargle, get done,
   get it over, get through, get through with, holystone, irrigate,
   lambaste, larrup, lather, launder, lave, lick, mop, overwhelm,
   perfect, rinse, rinse out, ritually immerse, round out, scour,
   scrub, scrub up, shampoo, shellac, shower, sluice, sluice out,
   soap, sponge, swab, syringe, terminate, toivel, top off, top out,
   tub, wash, wash out, wash up, wind up, wrap up