[Vocabulary] Slim chance vs fat chance

[patran]

Dear Teachers

Would like to know if slim chance (less likely to succeed) has an opposite meaning to fat chance (more likely to succeed?

Regards

Anthony the learner

 

[Barb_D]

No they mean the same except that "fat chance" is sarcastic.

There is a slim chance he will pass the exam.
Peter thinks he'll pass the exam? Ha! Fat chance!