Definition of there's no fool like an old fool in US English:

there's no fool like an old fool

phrase

proverb
  • The foolish behavior of an older person seems especially foolish as they are expected to think and act more sensibly than a younger one.

    • ‘There's no fool like an old fool, these old goats don't know how foolish they look.’
    • ‘Just goes to show, there's no fool like an old fool, especially an old fool that trusts the piskies.’
    • ‘As for Khan, there's no fool like an old fool.’