Ice formed at the bottom of the water; also called anchor-ice and ground-grue.

ice formed at the bottom of a body of water, esp. a lake or river; = ground-ice, n. 1.

(a) ice formed or lying at the bottom of a river or sea; anchor ice; (b) ice forming the lowest layer of a glacier or of a sheet of floating ice.

ground-ice.

= stock-frost n.

Ice formed at the bottom of a stream, anchor-ice. Also attributive.