"u-shaped"

Definition:

• Having the form of the letter U;
• of valleys, resembling a broad U in cross profile.

Web Definitions for u-shaped

• the entrances are roughly co-planar and horizontal, and are connected by a hole that bends at about a 180° angle.
  www.naturalarches.org/archinfo/classification.htm

• shaped in the form of the letter U
  wordnet.princeton.edu/perl/webwn