Merriam-Webster Collegiate Dictionary - pier

 noun  Etymology: Middle English per, from Old English, from Medieval Latin pera  Date: 12th century  1. an intermediate support for the adjacent ends of two bridge spans  2. a structure (as a breakwater) extending into navigable water for use as a landing place or promenade or to protect or form a harbor  3. a vertical structural support: as  a. the wall between two openings  b. pillar, pilaster  c. a vertical member that supports the end of an arch or lintel  d. an auxiliary mass of masonry used to stiffen a wall  4. a structural mount (as for a telescope) usually of stonework, concrete, or steel