Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
sterquĭlīnĭum (in MSS. also written stercŭl- and stercĭl-, Plaut. Pers. 3, 3, 3; Ter. Phorm. 3, 2, 41; Dig. 19, 1, 17, § 2), ii, n. (collat. form sterquĭlīnum, i, Phaedr. 3, 12, 1) [stercus], a dung-pit, laystall, mixen, Cato, R. R. 2, 3; Varr. 1, 13, 4; 1, 38, 3; Col. 1, 6, 21; 7, 5, 8; Phaedr. l. l.
As a term of reproach, Plaut. Pers. 3, 3, 3; id. Cas. 1, 26; Ter. Phorm. 3, 2, 41.