The Collaborative International Dictionary
Nitrifying
Nitrify \Ni"tri*fy\, v. t. [imp. & p. p. Nitrified; p. pr. & vb. n. Nitrifying.] [Niter + -fy: cf. F. nitrifer. See Niter.] (Chem.) To combine or impregnate with nitrogen; to convert, by oxidation, into nitrous or nitric acid; to subject to, or produce by, nitrification.
Wiktionary
nitrifying
a. Describing certain bacterium that oxidize ammonia to nitrite and nitrate in the soil