Glacial Trough – Erosion by glaciers in a "U" shape

(Pronounced gley-shuhl troff)

To remember the meaning of the term Glacial Trough, use the following mnemonic:

The farmer preferred his glass trough (glacial trough) to the pig's trough. The farmer's trough was "U" shaped and more comfortable.

A glacial trough is a valley widened and deepened by the erosive action of a glacier. The valley becomes U-shaped, rather than the V shape of a normal river valley. 

Glacial troughs tend to have steep, straight sides and flattish valley floors. As an example, the Norwegian Fjords are coastal troughs carved out by glaciers.