(noun)
the fine-grained wood obtained from birch trees, which is hard in texture and pale/light in color;
e.g. There is a desk made of birch in the corner of the room.
(noun)
a rod or a bundle of sticks made from birch wood, or a historical punishment in which a person is beaten with such an instrument;
e.g. They were threatened with the birch so that they remained disciplined.
(verb)
to beat or whip someone with or as if with a rod or bundle of sticks made of birch wood as a historical form of punishment;
e.g. The principal used to birch the students who had misbehaved.