The Collaborative International Dictionary
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.
To maintain (a living organism, such as microorganisms or a premature baby) under appropriate conditions, such as of temperature, humidity, or atmospheric composition, for growth; as, coliform bacteria grow best when incubated at 37[deg] C..
To develop gradually in some interior environment, until fully formed; as, the ideas for his book were incubating for two years before he began to write.
Wiktionary
vb. (present participle of incubate English)