German Slang for "Halt Dein Maul"
it´s like "shut the fuck up"
Uwe: Hey! You´re playing like a noob!
Marc: HDM bitch!
Honest direct message; commonly used on twitter or other social media sites.
SaltKing: hdm?
(N) Hot Dutty Mess. A person or a thing that is a shameful wreck and embarrassing to be around or look at.
Person A: " Did you see Shawndreequa's weave?"
Person B " Yee boom, it was an HDM"