Butment

Part of speech: noun (n.)

1. A buttress of an arch; the supporter, or that part which joins it to the upright pier.

2. The mass of stone or solid work at the end of a bridge, by which the extreme arches are sustained, or by which the end of a bridge without arches is supported. Butment cheek (Carp.), the part of a mortised timber surrounding the mortise, and against which the shoulders of the tenon bear. Knight.