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

WordNet (r) 3.0 (2006):

apex
    n 1: the highest point (of something); "at the peak of the
         pyramid" [syn: vertex, peak, apex, acme]
    2: the point on the celestial sphere toward which the sun and
       solar system appear to be moving relative to the fixed stars
       [syn: apex, solar apex, apex of the sun's way] [ant:
       antapex]

Moby Thesaurus II by Grady Ward, 1.0:

126 Moby Thesaurus words for "apex":
   L, Olympian heights, achievement, acme, aerial heights,
   alveolar ridge, alveolus, angle, apogee, arytenoid cartilages,
   attainment, back, bend, bifurcation, bight, blade, brow, cant, cap,
   capstone, chevron, climax, cloud nine, coin, consummation, corner,
   crank, crescendo, crest, crook, crotchet, crown, culmen,
   culmination, deflection, dizzy heights, dogleg, dorsum, edge,
   elbow, elevation, ell, eminence, ether, extreme limit, extremity,
   fork, furcation, hard palate, heaven, heavens, height, heights,
   high noon, highest pitch, highest point, hook, inflection, knee,
   larynx, last word, lift, limit, lips, maximum, meridian,
   mountaintop, nasal cavity, ne plus ultra, no place higher, nook,
   noon, noontide, oral cavity, palate, peak, pharyngeal cavity,
   pharynx, pinnacle, pitch, point, pole, prime, prominence, quoin,
   raise, realization, ridge, rise, rising ground, roof,
   seventh heaven, sky, soft palate, speech organ, spire, steep,
   stratosphere, summit, swerve, syrinx, teeth, teeth ridge, tip,
   tip-top, tongue, top, ultimate, upmost, upper extremity, uppermost,
   uprise, utmost, vantage ground, vantage point, veer, very top,
   vocal chink, vocal cords, vocal folds, vocal processes, voice box,
   zag, zenith, zig, zigzag



V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

APEX
       Advanced Packet EXchange


U.S. Gazetteer Places (2000):

Apex, NC -- U.S. town in North Carolina
   Population (2000):    20212
   Housing Units (2000): 8028
   Land area (2000):     10.536900 sq. miles (27.290445 sq. km)
   Water area (2000):    0.059767 sq. miles (0.154797 sq. km)
   Total area (2000):    10.596667 sq. miles (27.445242 sq. km)
   FIPS code:            01520
   Located within:       North Carolina (NC), FIPS 37
   Location:             35.731952 N, 78.852878 W
   ZIP Codes (1990):     27502
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Apex, NC
    Apex