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1 definition by corndonnus

An extremely socially-awkward person, that rarely involves themselves in the coversation and only contributes to the conversation by randomly commenting with a semi-muffled mumble (this usually is followed by a very, very awkward silence within the whole group of people).
That kid Nile came over for the first time last night and was being a mumblefuck the whole time.
by corndonnus March 11, 2010