It's American English slang and it's used to replace - 'am/is/are not'. For example, 'I ain't going'. I wouldn't recommend using it because it's bad English but it's important to know what it means :)

Just a historical note: 'Ain't' ain't American :) It's also used in many parts of the UK. In fact, 'ain't' was used in the British Isles, as an all-purpose negative, as far back as the early 18th century, . At that time, there was no social stigma attached to 'ain't', as it was part of the speech of all levels of society. It was only later that it became associated with lower social orders and uneducated classes. It can replace 'am not', 'is not', 'are not', 'has not' and 'have not'. You'll come across it frequently in song lyrics which are imitating informal speech. One reason for this is that it sometimes fits better with music than the more correct grammatical forms. 'Ain't nobody' means '[There] isn't anybody'. As you can see, 'ain't' even has its own grammar - with 'ain't', you need to have a negative form, whereas in standard grammar you can't have two negatives in the same construction. By the way, the use of 'ain't' is neither right nor wrong, neither good nor bad - it's simply different from standard English. And, like all non-standard language, there is a time and a place to use it. For example, some people might use it among friends in an informal situation, but not with their boss in an formal situation. Most native speakers say standard phrases using 'ain't' occasionally as a kind of joke, either to sound funny or folksy, or to emphasise a point such as how simple or obvious something is. But as native speakers, we have an instinctive sense of when it's appropriate to speak in non-standard English. It's a very subtle thing, and non-native speakers of English would be well advised to avoid using non-standard English unless their English is near-perfect and they're in the company of natives speaking the same way. I'm sure that there must be similar situations with regional or dialectal features of German.

ain't = is not/are not/am not

https://www.italki.com/question/263211#! https://www.italki.com/question/142832#!

Ain't ain't a real word, but it is colloquial English and important to understand. Ain't means = am not, however it remains the same for I, you, she, he, it, and they. So for example, you hear someone say "I ain't doing that." or "That ain't right." It often has a connotation of identifying the speaker as uneducated, or lower class. In addition, in the past it was used only in the South of the USA. Today it is not uncommon to hear in the Northeast, and although it often has the same connotation of being used by the uneducation, it can also be used for effect when the speaker feels angry, and indignant.