Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
grūmus, i, m., a little heap, hillock of earth: grumus terrae collectio minor tumulo, Paul. ex Fest. p. 96 Müll.; Att. ap. Non. 15, 24; Col. 2, 17, 4; Vitr. 2, 1; 8, 3; Auct. B. Hisp. 24.