Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. rŭmex, ĭcis, m., a missile weapon, similar to the sparum of the Gauls, Lucil. ap. Fest. pp. 270 and 271 Müll.; cf. Gell. 10, 25, 2.
2. rŭmex, ĭcis, f., sorrel, Plin. 11, 8, 8, § 18; 19, 12, 60, § 184; 20, 21, 85, § 231; Plaut. Ps. 3, 2, 26; Titin. ap. Non. 210, 4 (Com. Rel. p. 134 Rib.); Verg. M. 73.