Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. mento, ōnis, m. amplif. [mentum], one who has a long chin, long-chin, Arn. 3, 108.
2. Mento, ōnis, m. amplif. [id.], a Roman proper name. So C. Julius Mento, consul A. U. C. 323, Liv. 4, 26.