Meaning of “come on” - Learner’s Dictionary

come on

phrasal verb with come uk us /kʌm/ verb (past tense came, past participle come)

to start to happen or work:

The heating comes on at six in the morning.
I think I have a cold coming on.

to make progress:

How's your new novel coming on?
Come on! informal

B1 used to encourage someone to do something, to hurry, to try harder, etc:

Come on! We're going to be late.

used to tell someone that you do not agree with them, do not believe them, etc:

Come on Bob! You made the same excuse last week.

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