The Collaborative International Dictionary of English v.0.48:

Gorilla \Go*ril"la\, n. [An African word; found in a Greek
   translation of a treatise in Punic by Hanno, a Carthaginian.]
   (Zool.)
   A large, arboreal, anthropoid ape of West Africa. It is
   larger than a man, and is remarkable for its massive skeleton
   and powerful muscles, which give it enormous strength. In
   some respects its anatomy, more than that of any other ape,
   except the chimpanzee, resembles that of man. Goring

WordNet (r) 3.0 (2006):

gorilla
    n 1: largest anthropoid ape; terrestrial and vegetarian; of
         forests of central west Africa [syn: gorilla, Gorilla
         gorilla]

Moby Thesaurus II by Grady Ward, 1.0:

192 Moby Thesaurus words for "gorilla":
   Antaeus, Atlas, Barbary ape, Briareus, Brobdingnagian, Cain,
   Charles Atlas, Cyclops, Goliath, Hercules, Mafioso, Polyphemus,
   Samson, Superman, Tarzan, Titan, Young Turk, angwantibo,
   anthropoid ape, apache, ape, assassin, assassinator, aye-aye,
   baboon, battler, beast, beldam, belligerent, belted knight,
   berserk, berserker, bickerer, blade, bloodletter, bloodshedder,
   bomber, bravo, brawler, bruiser, brute, bully, bullyboy, burker,
   butcher, button man, cannibal, capuchin, chacma, chimpanzee,
   colossus, combatant, competitor, contender, contestant, cutthroat,
   demon, desperado, devil, disputant, dragon, drill, duelist,
   enforcer, entellus, eradicator, executioner, exterminator, fencer,
   feuder, fiend, fighter, fighting cock, fire-eater, firebrand,
   foilsman, fury, gamecock, garroter, giant, gibbon, gladiator, goon,
   guenon, guereza, gun, gunman, gunsel, hanuman, hardnose,
   hatchet man, head-hunter, hell-raiser, hellcat, hellhound, hellion,
   hit man, holy terror, homicidal maniac, homicide, hood, hoodlum,
   hooligan, hothead, hotspur, incendiary, jouster, killer, knight,
   langur, lemur, macaque, mad dog, madcap, man, man-eater,
   man-killer, mandrill, manslayer, marmoset, massacrer, matador,
   militant, monster, mountain gorilla, mug, mugger, murderer,
   muscle man, orang, orangutan, pesticide, plug-ugly, poison,
   poisoner, powerhouse, proboscis monkey, quarreler, rapist,
   revolutionary, rhesus, rioter, rival, rodman, rough, roughneck,
   rowdy, ruffian, sabreur, saki, savage, scrapper, scuffler,
   she-wolf, slaughterer, slayer, spitfire, squabbler, stalwart,
   strangler, strong arm, strong man, strong-arm man, strong-armer,
   struggler, swashbuckler, sword, swordplayer, swordsman, termagant,
   terror, terrorist, the mighty, the strong, thug, tiger, tigress,
   tilter, torpedo, tough, tough guy, tower of strength, trigger man,
   tussler, ugly customer, violent, virago, vixen, wild beast, witch,
   wolf, wrangler