THAT IS IT


Meaning of THAT IS IT in English

1.

this/that is the important point, reason, etc. :

That's just it—I can't work when you're making so much noise.

2.

this/that is the end :

I'm afraid that's it—we've lost.

Oxford Advanced Learner's English Dictionary.      Оксфордский английский словарь для изучающик язык на продвинутом уровне.