The Collaborative International Dictionary of English v.0.48:

Colossus \Co*los"sus\, n.; pl. L. Colossi, E. Colossuses.
   [L., fr. Gr. ?.]
   1. A statue of gigantic size. The name was especially applied
      to certain famous statues in antiquity, as the Colossus of
      Nero in Rome, the Colossus of Apollo at Rhodes.
      [1913 Webster]

            He doth bestride the narrow world
            Like a colossus.                      --Shak.
      [1913 Webster]

   Note: There is no authority for the statement that the legs
         of the Colossus at Rhodes extended over the mouth of
         the harbor. --Dr. Wm. Smith.
         [1913 Webster]

   2. Any man or beast of gigantic size.
      [1913 Webster]

WordNet (r) 3.0 (2006):

colossus
    n 1: someone or something that is abnormally large and powerful
         [syn: giant, goliath, behemoth, monster,
         colossus]
    2: a person of exceptional importance and reputation [syn:
       colossus, behemoth, giant, heavyweight, titan]

Moby Thesaurus II by Grady Ward, 1.0:

68 Moby Thesaurus words for "colossus":
   Antaeus, Atlas, Briareus, Brobdingnagian, Charles Atlas, Cyclops,
   Goliath, Hercules, Polyphemus, Samson, Superman, Tarzan, Titan,
   amazon, antenna tower, barbican, belfry, bell tower, bully,
   bullyboy, campanile, column, cupola, derrick, dome, fire tower,
   giant, gorilla, lantern, lighthouse, martello, martello tower,
   mast, minaret, monument, muscle man, obelisk, observation tower,
   pagoda, pilaster, pillar, pinnacle, pole, powerhouse, pylon,
   pyramid, shaft, skyscraper, spire, stalwart, standpipe, steeple,
   strong man, strong-arm man, stupa, television mast, the mighty,
   the strong, titan, tope, tough, tough guy, tour, tower,
   tower of strength, turret, water tower, windmill tower



The Free On-line Dictionary of Computing (30 December 2018):

Colossus

   (A huge and ancient statue on the Greek island of Rhodes).

   1.  The Colossus and Colossus Mark II computers used
   by Alan Turing at Bletchley Park, UK during the Second
   World War to crack the "Tunny" cipher produced by the Lorenz
   SZ 40 and SZ 42 machines.  Colossus was a semi-fixed-program
   vacuum tube calculator (unlike its near-contemporary, the
   freely programmable Z3).

   ["Breaking the enemy's code", Glenn Zorpette, IEEE Spectrum,
   September 1987, pp. 47-51.]

   2. The computer in the 1970 film, "Colossus: The Forbin
   Project".  Forbin is the designer of a computer that will run
   all of America's nuclear defences.  Shortly after being turned
   on, it detects the existence of Goliath, the Soviet
   counterpart, previously unknown to US Planners.  Both
   computers insist that they be linked, whereupon the two become
   a new super computer and threaten the world with the immediate
   launch of nuclear weapons if they are detached.  Colossus
   begins to give its plans for the management of the world under
   its guidance.  Forbin and the other scientists form a
   technological resistance to Colossus which must operate
   underground.

   The Internet Movie Database
   (http://www.imdb.com/title/tt0064177).

   (2007-01-04)