Source : Webster's Revised Unabridged Dictionary (1913)

Dewlap \Dew"lap`\, n. [Dew + lap to lick.]
   1. The pendulous skin under the neck of an ox, which laps or
      licks the dew in grazing.

   2. The flesh upon the human throat, especially when with age.
      [Burlesque]

            On her withered dewlap pour the ale.  --Shak.

Source : WordNet®

dewlap
     n : a hanging fold of loose skin on an elderly person's neck