Grumus, huius grumi, m. g. Colum. A barrow or hillocke of earth: a clotte, or cludder of any thing.Grumus salis. Plin. A great corne or cluster of salte.Grumulus huius grúmuli, m. g. pen. cor. Diminutiuum. Plin. A little hitsocke: a bedde in a garden rising like an hillocke.
Lewis and Short: Latin dictionary
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.