noun

1. a heavy structure supporting the spans of a bridge, esp., as distinguished from an abutment, one supporting the adjacent ends of two center spans of a long bridge
2. a structure built out over the water and supported by pillars or piles: used as a landing place, pleasure pavilion, etc.
3. Archit.
   1. a heavy column, usually square, used to support weight, as at the end of an arch
   2. the part of a wall between windows or other openings
   3. a reinforcing part built out from the surface of a wall

Etymology: ME per < ML pera, ult. < ? or akin to L petra, stone < Gr, rock