Real Dictionary

rabbet in American English
a groove or recess cut in the edge of a board, plank, etc. in such a way that another piece may be fitted into it to form a joint (rabbet joint)
to be joined by a rabbet
to cut a rabbet in
intransitive verb: to join by a rabbet
noun: a deep notch formed in or near one edge of a board, framing timber, etc., so that something else can be fitted into it or so that a door or the like can be closed against it
transitive verb: to cut a rabbet in (a board or the like)

rabbet in British English
to cut or form a rabbet in (timber)
noun: a recess, groove, or step, usually of rectangular section, cut into a surface or along the edge of a piece of timber to receive a mating piece