conversation thief 

The man or woman who routinely steamrolls their way into a private conversation and makes it their own, usually stealing one conversation partner and leaving the other feeling jilted.

Common incident in staff rooms, classrooms, etc., where interesting conversations are few and far between.

Esmeralda: "Oh you're so funny Rufus, I would be so unhappy without you to talk to."
Rufus: "So I was wondering, well if you're not too busy tonight, maybe we could-"
Jean-Claude: (pokes Esmerelda) "Traffic was bad this morning..."

Rufus:(looking totally cast aside)"That fucking Jean-Claude... what a conversation thief!"
Tom: "Yeah."

conversation thief by Thomas Harman February 28, 2009

Conversation Thief 

An individual who comes into a conversation and (Uncleverly) lays claim to all that was said. Like they brought all the information everyone was just discussing as their own. and worse?.....Believes that it were their own. this also can border line the grotesque acts of the "Conversation Vampire"!!!

Two people are standing there talking and a third person comes into the conversation, the third person nods head and agrees and within seconds begins to repeat what was said as it was their own idea, this is a "Conversation Thief". For it is obvious from the rest of the partakers in conversation that this individual lacks his or her own opinion, ideas, etc.

Conversation Thief by Stevjean February 11, 2014