The Collaborative International Dictionary of English v.0.48:

Apex \A"pex\, n.; pl. E. Apexes; L. Apices. [L.]
   1. The tip, top, point, or angular summit of anything; as,
      the apex of a mountain, spire, or cone; the apex, or tip,
      of a leaf.
      [1913 Webster]

   2. (Mining) The end or edge of a vein nearest the surface.
      [U.S.]
      [1913 Webster]

   Apex of the earth's motion (Astron.), that point of the
      heavens toward which the earth is moving in its orbit.
      [1913 Webster] aphaeresis