Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† grīphus, i, m., = γρῖφος (a net; hence transf.), an intricate or puzzling question, a riddle, enigma (post-class. and very rare): griphos dissolvere, Gell. 1, 4, 4; v. App. Flor. 9; Aus. Idyll. 11.