Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. mentum, i, n. [root men-, min-, to project; cf.: minae, minari, etc.], the chin of persons and animals; also, the chin with the hair that grows on it, the beard.
‡ 2. mentum dicebant, quod nos commentum, Paul. ex Fest. p. 124 Müll.