1 definition by Lady of the...
An action in which one is eating a delicious sandwich with mustard overflowing from the sides, becomes sloppy and leans over the keyboard. Mustard then drips on to the keyboard and, while trying desperately to wipe it off, one will press too many keys and freeze the computer.
"I was talking with Sandy on msn last night while eating a sandwich, and I totally did a mustard malfunction!"
by Lady of the... March 9, 2009