인마 or 임마 is a shortened form of 이놈아. The correct spelling is 인마, but it is often pronounced as 임마 and many native Koreans themselves are confused about the spelling as well. This word is used towards towards friends who are of similar age (usually not to someone who is older) and especially those who are younger. It is used the majority of the time towards males by males. If used to someone you are unfamiliar with, it can be considered offensive or disrespectful.
- 너나 잘해 인마.