Meaning of “king” - Learner’s Dictionary

king

noun [ C ] uk us /kɪŋ/
RULER

A2 a male ruler in some countries:

King Richard II
the kings and queens of England
BEST PERSON

the best or most important person in a particular activity:

He's the new king of pop music.
PLAYING CARD

a playing card with a picture of a king on it:

the king of spades

(Definition of “king” from the Cambridge Learner’s Dictionary © Cambridge University Press)