whin - What does it mean?

Noun

By this time he was cross the ford, / Whare in the snaw the chapman smoor'd; / And past the birks and meikle stane, / Whare drunken Charlie brak's neck-bane; / And through the whins , and by the cairn, / Whare hunters fand the murder'd bairn; / And near the thorn, aboon the well, / Whare Mungo's mither hang'd hersel.

And sometimes they clambered down […] and saw the whin bushes climb black the white hills beside them and far and away the blink of lights across the moors where folk lay happed and warm.

(Gray)