a. Recessing or sloping a wall back in successive courses; opposite of
corbel. ACSG, 1
b. A paste of clay or loam. Webster 2nd
c. The inward slope from bottom to top of the face of a wall.
d. A pile driven at an angle to widen the area of support and to resist
thrust. Nichols, 1
Dictionary of Mining, Mineral, and Related Terms