u-shaped

from WordNet (r) 3.0 (2006)

U-shaped
    adj 1: shaped in the form of the letter U

from The Collaborative International Dictionary of English v.0.48

U-shaped \U"-shaped`\, a.
   Having the form of the letter U; specif. (Phys. Geog.), of
   valleys, resembling a broad U in cross profile.
   [Webster 1913 Suppl.]