Hipparchus Syllabification: (Hip·par·chus)Pronunciation: /hiˈpärkəs/Definition of Hipparchus (circa 170-after 126 bc), Greek astronomer and geographer. He is best known for his discovery of the precession of the equinoxes and is credited with the invention of trigonometry. Hipparchus in other Oxford dictionaries Definition of Hipparchus in the British & World English dictionary