Source : Webster's Revised Unabridged Dictionary (1913)

Incubate \In"cu*bate\, v. i. & t. [imp. & p. p. {Incubated}; p.
   pr. & vb. n. {Incubating}.] [L. incubatus, p. p. incubare to
   lie on; pref. in- in, on + cubare to lie down. Cf. {Cubit},
   {Incumbent}.]
   To sit, as on eggs for hatching; to brood; to brood upon, or
   keep warm, as eggs, for the purpose of hatching.