A term used for an extremely annoying person, often with strange hair and/or weird habits of placing their hands behind their back.
Can also be used as a verb; to "Mehm" something is usually to fuck something up majorly.
Wow that kid is soooo annoying!
He must be a Mehm
(after ruining the punchline of a good joke)
You stupid little fuck! Way to Mehm my joke...