What is "abutments"

Usage examples of "abutments".

At every turn behind him lay more sandbagged abutments, every one of them manned.

Armed with that knowledge, she went to the abutments directly above the courtyard, made eldritch signs and symbols on the stone, wove rare gestures, chanted songs in the lost language of the Old Lords-and below her the sandy remains of the dead slowly parted.