From Longman Dictionary of Contemporary Englishthat’s itthat’s itspoken a) FINISH/COME TO AN ENDused to say that something is completely finished or that a situation cannot be changed That’s it, then. There’s nothing more we can do. b) PRAISEused to tell someone that they are doing something correctly Slowly ... slowly. Yeah, that’s it. c) (also that does it)REJECT/NOT ACCEPT used when you are angry about a situation and you do not want it to continue That’s it. I’m leaving. → it
Examples from the Corpus
that’s it• It rains till late February or early March, and that's it.• Sullen but accurate, spiky but efficient: that's it.• We get a custody order, and that's it.• Slowly...slowly... Yeah, that's it.• Clarence House has a reputation for giving half an hour and then that's it.• How many embalmers do you know who have 1 or 2 arterials, 1 cavity fluid and that's it.• Once you doubt my word, that's it.• One blooming lamp post at the corner and that's it.• Nothing more to do in here, Madeleine said: that's it, finished.• Power: that's it, I want power over my life.• OK, that's it. If you're not going to try, I'm not going to help you.that’s itthat’s itREJECT/NOT ACCEPT a) used to say that something is completely finished or that a situation cannot be changed That’s it, then. There’s nothing more we can do. b) used to tell someone that they are doing something correctly Slowly ... slowly. Yeah, that’s it. c) (also that does it) used when you are angry about a situation and you do not want it to continue That’s it. I’m leaving. → that 