to trick someone into believing something that is not true:
Even art experts were fooled.
you don't/can't fool me
You can't fool me with that old excuse.
be fooled by something
Don't be fooled by appearances.
fool somebody into doing something
I was fooled into believing their promises.
to try to make yourself believe something that you know is not really true:
It's no good fooling yourself. He's not coming back.
used to show that you do not believe what someone has told you:
'Look, we're doing our best to fix it.' 'Well, you could have fooled me.'
used to say that someone is not serious and is only pretending that something is true [= somebody is just kidding]:
Don't pay any attention to Henry. He's just fooling.
fool aroundphrasal verb
to waste time behaving in a silly way or doing things that are not important [= mess around]:
He always used to fool around in class.
to behave in a way which is careless and not responsible [= mess around]
fool around with
Some idiot's been fooling around with the electricity supply!
3 American English
to spend time doing something that you enjoy, but that does not have a particular purpose [= mess around]:
The boys were out in the yard, just fooling around.
to have a sexual relationship with someone else's wife, boyfriend etc [= mess around]:
She found out that he'd been fooling around behind her back.
fool with somethingphrasal verb
to touch or play with something, especially when you should not [= mess with something]:
Who's been fooling with the radio dial?
to become involved in something which could cause damage or be dangerous [= mess with something]