WordNet (r) 3.0 (2006):

top off
    v 1: finish up or conclude; "They topped off their dinner with a
         cognac"; "top the evening with champagne" [syn: top, top
         off]
    2: fill to the point of almost overflowing; "She topped off the
       cup"

Moby Thesaurus II by Grady Ward, 1.0:

97 Moby Thesaurus words for "top off":
   accomplish, brim, bring to completion, bring to fruition, bunker,
   button up, cap, carry to completion, cater, charge, chock,
   clean up, climax, close out, close up, coal, complete, conclude,
   congest, consummate, cram, crest, crowd, crown, culminate,
   detonate, eke out, end, explode, feed, fill, fill in, fill out,
   fill to overflowing, fill up, finalize, finish, finish off,
   finish up, forage, freight, frost, fuel, fuel up, fulfill,
   fulminate, gas, gas up, get done, get it over, get through,
   get through with, head, ice, jam, jam-pack, lade, load, make good,
   make up, mature, mop up, oil, outtop, overarch, overfill, overtop,
   pack, pad, peak, perfect, piece out, provender, provision, purvey,
   ram in, refill, refuel, replenish, round out, satiate, saturate,
   sell, stoke, stuff, supercharge, surfeit, surmount, terminate, tip,
   top, top out, victual, wad, weight, wind up, wrap up