noun
pile driver
A machine for driving piles into the ground, used in construction and civil engineering.
工事現場で杭打ち機が大きな音を立てていた。
The pile driver was making a loud noise at the construction site.
Compound of 杭 (kui, 'pile, stake') + 打ち (uchi, 'driving, hitting') + 機 (ki, 'machine').