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]WordNet (r) 3.0 (2006):
gargantuan adj 1: of great mass; huge and bulky; "a jumbo jet"; "jumbo shrimp" [syn: elephantine, gargantuan, giant, jumbo]