root cellar noun 1verb 1forms 3 noun1 •A structure built underground or partially underground and used to store vegetables, fruits, nuts, and other foods; it may be under a house or near one.Potatoes can keep if they are in a root cellar. verb1 •To cellar (food) in a root cellar.The growers will root cellar whatever portion of the crop does not sell at harvest time. formsroot cellared · root cellaring · root cellars