Talkjack
When you are telling a story or describing something to someone and another person jumps in and completely hijacks the story or description. The interruption is unwelcome and usually then takes the conversation off on a tangent to nowhere.
I was really getting into recounting my latest mishap story to a hottie at the bar when some rando dickhead decided to talkjack my story and starting telling us about the last time he fainted.