Have you ever looked at the base of a bridge or an arch? Have you ever wondered what that is called?
In engineering, abutment refers to the substructure at the end of a bridge span whereon the bridge's superstructure rests. Single-span bridges have abutments at each end which provide vertical and lateral support for the bridge, as well as acting as retaining walls to resist lateral movement of the earthen fill of the bridge approach. Multi-span bridges require piers to support ends of spans unsupported by abutments.
The term may also refer to the structure supporting one side of an arch or masonry used to resist the lateral forces of a vault. The word derives from the verb "abut", meaning to "touch by means of a mutual border".