<jargon> An unexpectedly bad situation, program, programmer, or person. Someone who habitually loses. (Even winners can lose occasionally). Someone who knows not and knows not that he knows not. Emphatic forms are "real loser", "total loser", and "complete loser" (but not **"moby loser", which would be a contradiction in terms).
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Nearby terms: Lorenz attractor « LORIA « lose « loser » losing » loss » lossage