Source : Webster's Revised Unabridged Dictionary (1913)

Inbreed \In*breed"\, v. t. [imp. & p. p. {Inbred}; p. pr. & vb.
   n. {Inbreeding}.] [Cf. {Imbreed}.]
   1. To produce or generate within. --Bp. Reynolds.

            To inbreed and cherish . . . the seeds of virtue.
                                                  --Milton.

   2. To breed in and in. See under {Breed}, v. i.

Source : WordNet®

inbreeding
     n : the act of mating closely related individuals