1.NounSomething very important or difficult; a matter of great concern; a considerable feat or achievement.
"It's a big deal to him to get this promotion.; It's no big deal if you don't finish it today.; Why do you always have to make such a big deal of tiny punctuation errors?"
2.NounSomeone very important; a VIP.
"She's a big deal in music in Spain."
3.InterjectionIndicates that something is not important or impressive; so what.
"He can run a mile in six minutes? Big deal! Some people can do it in four.; So you beat the worst team in the league. Big deal, call the TV crews."