* A typo: Perhaps the intended word was something similar like "nmh", which could be a misspelling of "nah" or "nmmh".
* An acronym or abbreviation: It could be a specific term used in a particular context or community that you're not familiar with.
* Random letters: It could be a nonsensical combination of letters with no meaning at all.
To understand the meaning, you'd need more context. Please provide the following information:
* Where did you see "nmjh"?: Was it in a text message, online forum, or somewhere else?
* What was the surrounding text or conversation?: This can give clues about the intended meaning.
With more information, I might be able to help you figure out what "nmjh" means.