What is "overhead engine"

Overhead \O`ver*head"\, adv. Aloft; above; in or attached to the ceiling or roof; in the story or upon the floor above; in the zenith.

While overhead the moon Sits arbitress.
--Milton.

Note: Also used adjectively; as, an overhead crane, gear, etc.

Overhead engine, a vertical steam engine in which the cylinder stands above the crank.

Overhead work, a general term in manufactories for countershafting and gearing, when overhead.

n. A vertical steam engine in which the cylinder stands above the crank.