Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† gnōmon, ŏnis, m., = γνώμων, the pin or style of a sundial, the gnomon, Plin. 2, 72, 74, § 182; Vitr. 1, 6; 9, 8; Mart. Cap. 6, 194.