Definition from Wiktionary, the free dictionary
- (idiomatic, informal) Something very important, difficult, or of concern.
- It's a big deal to him to get this promotion.
- It's no big deal if you don't finish.
something very important
- (idiomatic, informal, ironic) Indicates that something is not important or impressive; so what.
- He can run a mile in 15 minutes? Big deal! Some people can do it in four.