Commonly misinterpreted by users, the abbreviation can be harmful, even fatal.
'Well I do fucking mind you worthless shit! It’s my bling! Ima come around and cut your balls off and put them in your mouth!'
The previous was a common occurrence where Person B merely stated that he had not wasted much Person A's money, however, he got dead because he used the vague term, 'nm'.
Person 2: nm
Some people also use it as an abbreviation for "nevermind", but "nvm" is more popular.
Jill: nm u?
Jack: (starts talking about something)