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]