1 Greek & Roman Mythology a hero of superhuman strength and courage who performed twelve immense tasks or “labors” imposed on him and who after death was ranked among the gods. Greek name Heracles or Herakles.
• [as n.] (a Hercules) a man of exceptional strength or size.

2 Astronomy a large northern constellation, said to represent the kneeling figure of Hercules. It contains the brightest globular cluster in the northern hemisphere, but no bright stars.
• [as genitive] (Herculis) used with a preceding letter or numeral to designate a star in this constellation: the star Delta Herculis.