Learner's definition of ANYONE
Did anyone call?
If anyone calls, take a message.
I don't know how anyone can believe that.
An accident like that could happen to anyone.
I thought I heard someone outside, but there wasn't anyone there. [=no one was there]
You have to be a member to go there. They won't let just anyone in.
Everyone who's anyone [=every important or well-known person] was there.
She arrived 10 minutes before anyone else. [=before any other person]
— used when asking a question that could be answered by any one of the people in a group