Trail:

Glossary

Undercroft
Usually describes the vaulted room or rooms beneath the main room or rooms of a medieval house. Compare crypt.
Undershot water wheel
One turned by the momentum of the water passing beneath. Compare breastshot, overshot and pitchback.
Univallate
Of a hill-fort: defended by one concentric bank and ditch.
Upper cruck
A type of timber construction in which curving paired members (blades) are supported on a tie-beam and rise to the apex.