TROUGH, n. trauf.

1. A vessel hollow longitudinally, or a large log or piece of timber excavated longitudinally on the upper side used for various purposes.
2. A tray. This is the same word dialectically altered.
3. A canoe the rude boat of uncivilized men.
4. The channel that conveys water, as in mills.

The trough of the sea, the hollow between waves.