Definition of I'll be damned
informal + impolite
1
—used to show that one is very surprised about something
- Well I'll be damned! Our team actually won!
- I spent an hour putting the machine together and I'll be damned if it didn't fall apart as soon as I tried to use it.
- I told them they wouldn't enjoy the trip but damned if they didn't come anyway.
2
—used to say that one cannot or will not do something —+ if
- I'll be damned if I can remember where I left my keys.
- I'll be damned if I'm going to eat any more of that disgusting food.
Writing? Check your grammar now!