Source : Webster's Revised Unabridged Dictionary (1913)

Kumquat \Kum"quat\, n. [Chin. kin keu.] (Bot.)
   A small tree of the genus {Citrus} ({C. Japonica}) growing in
   China and Japan; also, its small acid, orange-colored fruit
   used for preserves.

Source : WordNet®

kumquat
     n 1: any of several trees or shrubs of the genus Fortunella
          bearing small orange-colored edible fruits with thick
          sweet-flavored skin and sour pulp [syn: {cumquat}, {kumquat
          tree}]
     2: small oval citrus fruit with thin sweet rind and very acid
        pulp