loch I. \ˈläk, ˈläḵ\noun (-s) Etymology: Middle English (Scots) louch, locht, from Scottish Gaelic loch; akin to Old Irish loch lake, pond — more at lake 1.Scotland: lake 2.Scotland: a bay or arm of the sea especially when nearly landlocked II. \ˈläk\noun (-s) Etymology: origin unknown Britain: a fissure or void cavity in a mineral vein especially of a lead mine