the means of "이쟎아' is 'is'
but you usally use this '이쟎아' when you have opposing views
for example..
there are two guys, A and B
A: hey, Let's go to museum
B: Today is sunday! (museum is not open today)
A: 박물관 가자!
B: 오늘은 일요일 이쟎아!
A:Hey why didn't you come yesterday, i'was wating for you!
B:Our meeting day is today!
A: 야. 너외 어제 안왔어, 기다렸쟎아..
B: 우리 만나기로 한날은 오늘 이쟎아!