The Collaborative International Dictionary of English v.0.48:

Kilogram \Kil"o*gram\, Kilogramme \Kil"o*gramme\, n. [F.
   kilogramme; pref. kilo- (fr. Gr. chi`lioi a thousand ) +
   gramme. See 3d Gram.]
   A measure of mass and weight, being a thousand grams, equal
   to 2.2046226 pounds avoirdupois (15,432.34 grains). It is
   nearly equal to the mass of a cubic decimeter of distilled
   water at the temperature of maximum density, or 39[deg]
   Fahrenheit. See 3rd gram.
   [Webster 1913 Suppl.] Kilogrammeter

WordNet (r) 3.0 (2006):

kilogram
    n 1: one thousand grams; the basic unit of mass adopted under
         the Systeme International d'Unites; "a kilogram is
         approximately 2.2 pounds" [syn: kilogram, kg, kilo]