himmeldorf

an adjective that describes a person that eavesdrops on, and then joins a conversation that has nothing to do with them.
It is typically used as an insult to that person, to tell them to get the fuck out of your private conversations.

Joe: Yo dude I totally fucked your sister last night...
Dude: Sucks for you, she totally has chlamydia
Joe: What?!??
Dude: psyche!
Random Himmeldorf: So then your sister doesn't have chlamydia?
Joe: stfu himmeldorf stop eavesdropping on us