king
noun [ C ]
uk/kɪŋ/ usa person, company, or organization that is thought to be the best or most successful:
It is widely considered to be king of the supermarket chains.
sb/sth is king
used to say that someone or something is the most important part of something or has the most influence:
In mergers and acquisitions, cash is king.
They all followed the principle that the customer is king.
Media executives are fond of saying that content is king.