Lewis & Short

Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.

Mărăthos or -us, i, f., = Μάραθος, an ancient Phœnician city, opposite the island of Arados, near the modern Ainel-Hye, Mel. 1, 12, 3; Plin. 5, 20, 17, § 78; Curt. 4, 1, 6.
Hence, Mărăthēnus, a, um, adj., of or from Marathos, Marathene: Menelaüs, a rhetorician from Marathos, Cic. Brut. 26, 100 Meyer.