(climbing) A form of bouldering performed on a (usually wooden) climbing wall compact enough to fit at home but covered with many climbing holds, often done as practice for standard bouldering.

Wearing board shorts.

(computing, historical) A type of computer system, now largely obsolete, used to exchange messages and data over a telecommunications network.

(idiomatic) All over the map.

(electronics) A flat board that holds chips and other electronic components in layers that interconnect via copper pathways, often called traces.

(idiomatic) Back to the beginning following an unsuccessful attempt.

(construction) A rigid board insulation generally composed of perlite or wood fiberboard factory bonded to polyisocyanurate or polystyrene.

(obsolete, nautical) To act in an unusual manner; to behave differently.

plural of printed circuit board

plural of bulletin board system