Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† ĕpos (occurring only in the nom. and acc.), n., = ἔπος, a heroic poem, an epic; nom., Hor. S. 1, 10, 43; acc., Mart. 12, 95; Aus. Prof. 5, 10.