Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
concŭbĭtor, ōris, m. [concubo], a bed-fellow ( = concubinus; concubitor, συγκοιμητής, Gloss.; eccl. Lat.), Salv. 7, p. 251; Vulg. 1. Cor. 6, 10.