■ contraction informal
1》 am not; are not; is not.
2》 has not; have not.
Usage
In modern English the use of ~ is non-standard, despite it being widespread in many dialects and in informal speech.
AIN'T
Meaning of AIN'T in English
Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004