WordNet (r) 3.0 (2006):

maximal
    adj 1: the greatest or most complete or best possible; "maximal
           expansion"; "maximum pressure" [syn: maximal,
           maximum] [ant: minimal, minimum]

Moby Thesaurus II by Grady Ward, 1.0:

90 Moby Thesaurus words for "maximal":
   abounding, abundant, acmatic, affluent, all-sufficing, ample,
   apical, aplenty, best, bottomless, bounteous, bountiful, capital,
   chief, consummate, copious, diffuse, effuse, epidemic, exhaustless,
   extravagant, exuberant, fat, fertile, first-class, first-rate,
   flush, full, galore, generous, greatest, head, headmost, highest,
   in plenty, in quantity, inexhaustible, lavish, liberal, luxuriant,
   many, maximum, meridian, meridional, most, much, numerous, opulent,
   outside, overflowing, overmost, paramount, plenitudinous,
   plenteous, plentiful, plenty, preeminent, prevailing, prevalent,
   prodigal, productive, profuse, profusive, rampant, replete, rich,
   rife, riotous, running over, summital, superabundant, superlative,
   supreme, teeming, tip-top, top, top-notch, topmost, ultimate,
   upmost, uppermost, utmost, vertical, wealthy, well-found,
   well-furnished, well-provided, well-stocked, wholesale, zenithal