1) Engineering vehicle 
A pile driver is a mechanical device used to drive piles (poles) into soil to provide foundation support for buildings or other structures. The term is also used in reference to members of the construction crew that work with pile-driving rigs. One traditional type of pile driver includes a heavy weight placed between guides so that it is able to ...
(from the article `pile`) ...piles. On unstable soils, piles are indispensable building supports and may also be used on stable ground when exceptionally large structural ...
Pile-driver is British slang for a male homosexual.
[n] - a machine that drives piling into the ground
noun a machine that drives piling into the ground