The Collaborative International Dictionary of English v.0.48:

Coxcomb \Cox"comb`\ (k?ks"k?m`), n. [A corrupted spelling of
   cock's comb.]
   1.
      (a) A strip of red cloth notched like the comb of a cock,
          which licensed jesters formerly wore in their caps.
      (b) The cap itself.
          [1913 Webster]

   2. The top of the head, or the head itself.
      [1913 Webster]

            We will belabor you a little better,
            And beat a little more care into your coxcombs.
                                                  --Beau & Fl.
      [1913 Webster]

   3. A vain, showy fellow; a conceited, silly man, fond of
      display; a superficial pretender to knowledge or
      accomplishments; a fop.
      [1913 Webster]

            Fond to be seen, she kept a bevy
            Of powdered coxcombs at her levee.    --Goldsmith.
      [1913 Webster]

            Some are bewildered in the maze of schools,
            And some made coxcombs, nature meant but fools.
                                                  --Pope.
      [1913 Webster]

   4. (Bot.) A name given to several plants of different genera,
      but particularly to Celosia cristata, or garden
      cockscomb. Same as Cockscomb.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Cockscomb \Cocks"comb`\ (k[o^]ks"k[=o]m`), n. [1st cock, n. +
   comb crest.]
   1. See Coxcomb.
      [1913 Webster]

   2. (Bot.) A plant (Celosia cristata), of many varieties,
      cultivated for its broad, fantastic spikes of brilliant
      flowers; -- sometimes called garden cockscomb. Also the
      Pedicularis, or lousewort, the Rhinanthus
      Crista-galli, and the Onobrychis Crista-galli.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Celosia cristata
    n 1: garden annual with featherlike spikes of red or yellow
         flowers [syn: cockscomb, common cockscomb, Celosia
         cristata, Celosia argentea cristata]