Cairn

Webster's Dictionary

(1): (n.) A rounded or conical heap of stones erected by early inhabitants of the British Isles, apparently as a sepulchral monument.

(2): (n.) A pile of stones heaped up as a landmark, or to arrest attention, as in surveying, or in leaving traces of an exploring party, etc.

The Nuttall Encyclopedia

A heap of stones often, though not always, loosely thrown together, generally by way of a sepulchral monument, and it would seem sometimes in execration of some foul deed.