Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
obnoxĭo, 1, v. a. [obnoxius], to render subject or obnoxious to any thing (postclass.): et alienis semet noxiis obnoxiantes, Claud. Mam. Stat. Anim. 2, 9.