WordWeb Online

1. The highest point (of something)
   "at the apex of the pyramid";
   - vertex, peak, acme
    
2. The point on the celestial sphere toward which the sun and solar system appear to be moving relative to the fixed stars
   - solar apex, apex of the sun's way

Derived forms: apices, apexes

Type of: celestial point, extreme, extreme point, extremum

Antonym: antapex

Part of: celestial sphere, empyrean, firmament, heavens, sphere, vault of heaven, welkin

Encyclopedia: Apex, Nevada