WordNet (r) 3.0 (2006):

fill up
    v 1: make full, also in a metaphorical sense; "fill a
         container"; "fill the child with pride" [syn: fill, fill
         up, make full] [ant: empty]
    2: become full; "The pool slowly filled with water"; "The
       theater filled up slowly" [syn: fill, fill up] [ant:
       discharge, empty]
    3: fill or stop up; "Can you close the cracks with caulking?"
       [syn: close, fill up]
    4: eat until one is sated; "He filled up on turkey" [syn: fill
       up, fill]

Moby Thesaurus II by Grady Ward, 1.0:

140 Moby Thesaurus words for "fill up":
   accommodate, afford, allay, atone, bar, bind, block, block up,
   blockade, brim, bung, bunker, cater, caulk, charge, chink, chock,
   choke, choke off, choke up, clog, clog up, clothe, cloy, coal,
   compensate, congest, constipate, contribute, cork, cover, cram,
   crowd, dam, dam up, detonate, do penance, donate, endow, engorge,
   expiate, explode, feed, fill, fill in, fill to overflowing, find,
   forage, foul, freight, fuel, fuel up, fulminate, fund, furnish,
   gas, gas up, give, give and take, glut, gorge, indemnify, invest,
   jade, jam, jam-pack, keep, lade, load, maintain, make amends,
   make available, make compensation, make good, make provision for,
   make up for, obstipate, obstruct, oil, overdose, overfeed,
   overfill, overgorge, oversaturate, overstuff, pack, pad, pall,
   pay back, plug, plug up, prepare, present, provender, provide,
   provide for, provision, purvey, ram in, recompense, recruit,
   rectify, refuel, repay, replenish, retaliate, sate, satiate,
   satisfy, saturate, sell, set right, shallow, shoal, silt up, slake,
   spile, stanch, stay, stench, stock, stoke, stop, stop up, stopper,
   stopple, store, stuff, stuff up, subsidize, supercharge,
   supersaturate, supply, support, surfeit, top off, victual, wad,
   weight, yield