Ōs or Ō'sar1, n.
n. (Geol.) (a.) A low ridge of stone or gravel, supposed to be a moraine formed by glaciers; — so called in Scandinavia. (b.) A similar ridge, supposed to be of moraine origin, in other countries. (c.) A ridge of sand and gravel, formed under water, by currents piling up the materials behind some obstruction.