A door rebate is an alternate British term for a rabbet, a deep groove or notch cut into the edge of building material such as wood. The groove allows a tight fit with other objects that are placed against or into the material.
A rabbet may be cut to accommodate a pane of glass when building window frames. Rabbets are also used to form joints with other pieces of the same material. In that particular case, the rabbet may also be called a dado. Dados are grooves or slots that are specifically for stationary joints. Door rebates or rabbets are associated with door jambs, the vertical sides of a door frame.