Hmm...neither the Oxford English Dictionary (OED) nor m-w.com have a listing for gargantuas, spelled with an "s". Could "gargantuas" be the plural of "gargantua"?
If so, a "gargantua," according to the OED, is a giant -- one who resembles the famous Gargantua in Rabelais' story Gargantua and Pantagruel. You can read the book online (translated into English) at Project Gutenberg.
IMDB also has a listing for "Gargantua," but from the reviews the less said about that, the better.