Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† sīrus, i, m., = σιρός, a pit to keep corn in, an underground granary (cf. cumera), Plin. 18, 30, 73, § 306; Col. 1, 6, 15; Curt. 7, 4, 24; cf. Auct. B. Afr. 65; Vitr. 6, 8 (Varr. R. R. 1, 57 and 63, written as Greek).