Meaning of “challenge” - Learner’s Dictionary

challenge

noun uk us /ˈtʃælɪndʒ/
DIFFICULT [ C, U ]

B1 something that is difficult and that tests someone's ability or determination:

Finding a decision that pleases everyone is the challenge which now faces the committee.
It was the element of challenge which attracted me to the job.
INVITATION [ C ]

an invitation to compete in a game or a fight:

I'm sure Paul will race you. He never refuses a challenge.
DISAGREEMENT [ C ]

an expression of disagreement with ideas, rules, or someone's authority:

a challenge to the authority of the President

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