Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† sĭsymbrĭum, ii, n., = σισύμβριον, a fragrant herb sacred to Venus, perh. wildthyme or mint, Plin. 20, 22, 91, § 247; 19, 8, 55, § 172; 19, 10, 57, § 176; Ov. F. 4, 869.