noun

• (Ireland, Scotland) A lake.
  "The greater part of Leuchars Loch belonged to the Inneses of Leuchars, Cotts to the Inneses of Innes; and while thus poſſeſſed, many unſucceſsful attempts to drain both, by canals, to the river Loſſie, ſeem to have been made. […] [A] very ordinary fall of rain raiſes it [the river] far beyond its natural bounds; and the immediate conſequence of ſuch floods, was, the ſpeat-water flowing into thoſe lochs, by the canal, and covering the adjacent meadows."
• (Ireland, Scotland) A bay or arm of the sea.
  "It is well known, for instance, that the superiority of the herrings caught in the inland sea-lochs of Scotland is owing to the fish finding there a better feeding-ground than in the large and exposed open bays. Look, for instance, at Lochfyne: the land runs down to the water's edge, and the surface water or drainage carries with it rich food to fatten the loch, and put flesh on the herring; and what fish is finer, I would ask, than a Lochfyne herring?"