Noun - one who overhears your conversation and inserts their own personal thoughts into said conversation without invitation. Often the hi-jacker's words will have no relevance to your conversation and has only served to take said conversation on a 20 minute tangent to nowhere.
Verbal piracy at its apex, bringing your conversation to its nadir.
"So I was discussing the bar scene at my alma-mater with Jen when Elle hi-jacked our conversation and we ended up talking about brownies for twenty minutes. Dammit."
-"Bro she is a conversation hi-jacker, you gotta be careful."
Acronym - short for Drunk Loud Talker, one who's voice volume increases by 15 decibels or more upon consumption of alcoholic substances. Pitch and tone can remain heightened or flat, however rate of delivery will increase as well.