pile driver

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A machine that drives a pile by raising a weight between guideposts and dropping it on the head of the pile.

from The Century Dictionary.

• noun A workman occupied in driving piles.
• noun A machine or contrivance, usually worked by steam, for driving piles.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A machine for forcing a pile, a long beam, into the ground as part of the construction of a foundation; usually by raising a weight and then dropping it on the beam.
• noun A person who hits or attacks forcefully or powerfully.
• adjective forceful

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a machine that drives piling into the ground