Definition of you could have fooled me! in English:

you could have fooled me!

phrase

  • Used to express cynicism or doubt about an assertion.

    ‘‘Fun, was it? Well, you could have fooled me!’’
    • ‘Well, with that act you pulled off, you could have fooled me!’
    • ‘Well, you could have fooled me -- the humor in this book demonstrates that you are indeed a funny person.’