The Collaborative International Dictionary of English v.0.48:

Kitten \Kit"ten\ (k[i^]t"t'n), n. [OE. kiton, a dim. of cat; cf.
   G. kitze a young cat, also a female cat, and F. chaton, dim.
   of chat cat, also E. kitling. See Cat.]
   A young cat.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Kitten \Kit"ten\, v. t. & i. [imp. & p. p. Kittened; p. pr. &
   vb. n. Kittening.]
   To bring forth young, as a cat; to bring forth, as kittens.
   --Shak. --H. Spencer.
   [1913 Webster]

WordNet (r) 3.0 (2006):

kitten
    n 1: young domestic cat [syn: kitten, kitty]
    v 1: have kittens; "our cat kittened again this year"