The Collaborative International Dictionary of English v.0.48:

Hercules \Her"cu*les\, n.
   1. (Gr. Myth.) A hero, fabled to have been the son of Jupiter
      and Alcmena, and celebrated for great strength, esp. for
      the accomplishment of his twelve great tasks or "labors."
      [1913 Webster]

   2. (Astron.) A constellation in the northern hemisphere, near
      Lyra.
      [1913 Webster]

   Hercules' beetle (Zool.), any species of Dynastes, an
      American genus of very large lamellicorn beetles, esp.
      Dynastes hercules of South America, which grows to a
      length of six inches.

   Hercules powder, an explosive containing nitroglycerin; --
      used for blasting.
      [1913 Webster] Hercules'-club
      Hercules'-club

WordNet (r) 3.0 (2006):

Hercules
    n 1: (classical mythology) a hero noted for his strength;
         performed 12 immense labors to gain immortality [syn:
         Hercules, Heracles, Herakles, Alcides]
    2: a large constellation in the northern hemisphere between Lyra
       and Corona Borealis