Source : Webster's Revised Unabridged Dictionary (1913)

Pinnacle \Pin"na*cle\, n. [OE. pinacle, F. pinacle, L.
   pinnaculum, fr. pinna pinnacle, feather. See {Pin} a peg.]
   1. (Arch.) An architectural member, upright, and generally
      ending in a small spire, -- used to finish a buttress, to
      constitute a part in a proportion, as where pinnacles
      flank a gable or spire, and the like. Pinnacles may be
      considered primarily as added weight, where it is
      necessary to resist the thrust of an arch, etc.

            Some renowned metropolis With glistering spires and
            pinnacles around.                     --Milton.

   2. Anything resembling a pinnacle; a lofty peak; a pointed
      summit.

            Three silent pinnacles of aged snow.  --Tennyson.

            The slippery tops of human state, The gilded
            pinnacles of fate.                    --Cowley.

Pinnacle \Pin"na*cle\, v. t. [imp. & p. p. {Pinnacled}; p. pr. &
   vb. n. {Pinnacling}.]
   To build or furnish with a pinnacle or pinnacles. --T.
   Warton.

Source : WordNet®

pinnacle
     n 1: (architecture) a slender upright spire at the top of a
          buttress of tower
     2: the highest level or degree attainable; "his landscapes were
        deemed the acme of beauty"; "the artist's gifts are at
        their acme"; "at the height of her career"; "the peak of
        perfection"; "summer was at its peak"; "...catapulted
        Einstein to the pinnacle of fame"; "the summit of his
        ambition"; "so many highest superlatives achieved by man";
        "at the top of his profession" [syn: {acme}, {height}, {elevation},
         {peak}, {summit}, {superlative}, {top}]
     3: a lofty peak
     v 1: surmount with a pinnacle; "pinnacle a pediment"
     2: raise on or as if on a pinnacle; "He did not want to be
        pinnacled"