Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
prŏhĭbĭtor, ōris, m. [prohibeo], a withholder, restrainer, preventer (post-class.): valetudinum pessimarum, Arn. 7, 249; Amm. 21, 12, 9; 24, 4, 23; App. de Deo Socr. p. 52 med.