Source : Webster's Revised Unabridged Dictionary (1913)

Crest \Crest\ (kr[e^]st), n. [OF. creste, F. cr[^e]te, L.
   crista.]
   1. A tuft, or other excrescence or natural ornament, growing
      on an animal's head; the comb of a cock; the swelling on
      the head of a serpent; the lengthened feathers of the
      crown or nape of bird, etc. --Darwin.

            [Attack] his rising crest, and drive the serpent
            back.                                 --C. Pitt.

   2. The plume of feathers, or other decoration, worn on a
      helmet; the distinctive ornament of a helmet, indicating
      the rank of the wearer; hence, also, the helmet.

            Stooping low his lofty crest.         --Sir W.
                                                  Scott.

            And on his head there stood upright A crest, in
            token of a knight.                    --Gower.

   3. (Her.) A bearing worn, not upon the shield, but usually
      above it, or separately as an ornament for plate,
      liveries, and the like. It is a relic of the ancient
      cognizance. See {Cognizance}, 4.

   4. The upper curve of a horse's neck.

            Throwing the base thong from his bending crest.
                                                  --Shak.

   5. The ridge or top of a wave.

            Like wave with crest of sparkling foam. --Sir W.
                                                  Scott.

   6. The summit of a hill or mountain ridge.

   7. The helm or head, as typical of a high spirit; pride;
      courage.

            Now the time is come That France must vail her lofty
            plumed crest.                         --Shak.

   8. (Arch.) The ornamental finishing which surmounts the ridge
      of a roof, canopy, etc.

            The finials of gables and pinnacles are sometimes
            called crests.                        --Parker.

   9. (Engin.) The top line of a slope or embankment.

   {Crest tile}, a tile made to cover the ridge of a roof,
      fitting upon it like a saddle.

   {Interior crest} (Fort.), the highest line of the parapet.

Crest \Crest\, v. t. [imp. & p. p. {Crested}; p. pr. & vb. n.
   {Cresting}.]
   1. To furnish with, or surmount as, a crest; to serve as a
      crest for.

Crest \Crest\ (kr[e^]st), v. i.
   To form a crest.

Source : WordNet®

crest
     n 1: the top line of a hill, mountain, or wave
     2: the top point of a mountain or hill; "the view from the peak
        was magnificent"; "they clambered to the summit of
        Monadnock" [syn: {peak}, {crown}, {top}, {tip}, {summit}]
     3: the center of a cambered road [syn: {crown}]
     4: (heraldry) in medieval times, an emblem used to decorate a
        helmet
     5: a showy growth of e.g. feathers or skin on the head of a
        bird or other animal
     v 1: lie at the top of; "Snow capped the mountains" [syn: {cap}]
     2: reach a high point; "The river crested last night"