1. Stop it!; Stop doing that. (Usually Come on!)
> Mary: Are you really going to sell your new car? Sally: Come on! How dumb do you think I am?

2. please oblige me.
> Mother: Sorry. You can't go! Bill: Come on, let me go to the picnic!

3. to hurry up; to follow someone.
> If you don't come on, we'll miss the train.

4. [for electricity or some other device] to start operating.
> After a while, the lights came on again.

5. to walk out and appear on stage.
> You are to come on when you hear your cue.

6. [for a pain] to begin hurting; [for a disease] to attack someone.
> The pain began to come on again, and Sally had to lie down.

7. [for a program] to be broadcast on radio or television.
> The news didn't come on until an hour later.