Gargantuan

from WordNet (r) 3.0 (2006)

gargantuan
    adj 1: of great mass; huge and bulky; "a jumbo jet"; "jumbo
           shrimp" [syn: {elephantine}, {gargantuan}, {giant},
           {jumbo}]

from The Collaborative International Dictionary of English v.0.48

Gargantuan \Gar*gan"tu*an\ (?; 135), a. [From Gargantua, an
   allegorical hero of Rabelais.]
   Characteristic of Gargantua, a gigantic, wonderful personage;
   enormous; prodigious; inordinate.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

51 Moby Thesaurus words for "Gargantuan":
      Atlantean, Brobdingnagian, Cyclopean, Herculean, Homeric, abysmal,
      amplitudinous, astronomic, astronomical, awesome, boundless, bulky,
      colossal, cosmic, elephantine, enormous, epic, extensive, galactic,
      giant, giantlike, gigantic, heroic, huge, immeasurable, immense,
      infinite, jumbo, king-size, large, mammoth, massive, massy, mighty,
      monster, monstrous, monumental, mountainous, outsize, overgrown,
      prodigious, profound, sizable, spacious, stupendous, titanic,
      towering, tremendous, vast, voluminous, weighty