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"

Moby Thesaurus II by Grady Ward, 1.0:

97 Moby Thesaurus words for "kitten":
   Cheshire cat, Chinchilla cat, Maltese cat, alley cat, bairn,
   be confined, bear, bear a child, bear young, birdling, blue cat,
   calf, calico cat, calve, cast, cat, catling, cherub, chick,
   chickling, chicky, child, chit, colt, cub, darling, dogie, drop,
   duckling, farrow, fawn, feline, fledgling, foal, fryer, gib,
   gib-cat, give birth, gosling, grimalkin, have, have a baby,
   have young, house cat, innocent, kid, kit, kitling, kitty,
   kitty-cat, labor, lamb, lambkin, lie in, litter, little bugger,
   little fellow, little guy, little innocent, little one, little tad,
   little tot, mite, mouser, nest, nestling, nipper, offspring,
   peewee, piglet, pigling, polliwog, pullet, pup, puppy, puss, pussy,
   pussycat, shaver, shoat, silver cat, tabby, tabby cat, tad,
   tadpole, throw, tiger cat, tom, tomcat, tortoise-shell cat, tot,
   travail, weaner, wee tot, whelp, yean, yeanling