Dictionary.net

A term for a late geological formation in the superficial drift, generally consisting of a long linear ridge of sand and gravel, including pieces of considerable size; the materials are derived from the waste of till or boulder-clay, and their arrangement took place probably under water over which icebergs floated, for in Sweden particularly rough erratic blocks are often deposited on the eskar. Called in Scotland a KAIM; called also AESAR, OS, and OSAR.