Definition of cool it! in English:

cool it!

phrase

informal
  • Behave in a less excitable manner.

    ‘cool it and tell me why you're so ecstatic’
    • ‘If you're not careful you'll be too tired to even lift the crown, cool it!’
    • ‘I got a certificate saying I've been admitted to the bar, and I've even got a wig, so cool it!’
    • ‘I ask him to cool it, but he doesn't calm down that easily, so I think it's about something else.’