(noun)
a man who served a feudal lord or rule in the Middle Ages and who is made a mounted soldier or given a military rank for his service;
e.g. He made a knight and placed in charge of the protection of the land.
(noun)
in literary usage, a man who is devoted to some cause or to the service of a lady (as her companion or attendant);
e.g. He became her knight as she began to succeed in her career.
(noun)
in chess, each of the two playing pieces on each side that is shaped like the head of a horse and that moves in an 'L' shaped path;
e.g. He moved his knight towards his opponent's queen.
(verb)
to confer the honor of being a knight on someone;
e.g. The leaders voted to knight the author for his contributions.