An esker is a long, winding RIDGE of gravel and other sedimentary material that was formed by a stream or river of meltwater during the last Ice Age. It is usually found in areas where glaciers once existed. The term esker is derived from the Irish word eiscir, which means 'RIDGE'. The crossword solutions for the term esker are RIDGE (5 letters) and OSE (3 letters). Ose is an Old Norse word meaning 'riverbed'.