Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. aggestus (adg-), ūs, m. [aggero], a bearing or carrying to a place, a collecting, an accumulation, collection (post-Aug. and rare): pabuli, materiae, lignorum, Tac. A. 1. 35: copiarum, id. H. 3, 60: harenae, Aur. Vict. Ep. 3.
2. aggestus, i, m., or aggestum (adg-), i, n. [aggero], an elevation formed like a dike or mound: prunas unius aggesti inseruere juncturis, Amm. 20, 11; 19, 8.