U KITCHEN:
A kitchen design where the countertops and appliances are arranged in the shape of a rectangular U, affording no through traffic.

UNDERCOAT:
Any coating that has been applied prior to the finishing coat of a paint job. Often referred to as the primer coat.

UNDERLAY: (or underlayment)
Any material placed under flooring, carpets or shingles to provide a smooth even surface for the finish materials.