To "cock-block" someone. Mostly used in french, and although usually meant to describe a female who lafarges a man, the sexes can be interchanged. This means that the most common use would be for a woman who lafarges a man who is trying to "get with" either her or another female. It can however also mean a woman who lafarges another woman, a man who lafarges a woman, or a man who lafarges a man.

This word can be used to describe actions both with negative and positive results (i.e. if the dude was a big douche-bag, he can still be lafarged).

Also, lafarging someone can be intentional or accidental.
"Dude, the girl totaly just lafarged me. I was so close to hooking up with Cindy, but the lafargeuse came in and started talking about forest fires...MOOD KILLER!"
by L.J.R. October 14, 2009
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Boy 1: "i got herpes from that lafarge girl"
Boy 2: "She gave me the clap a month ago!"
by yabz August 17, 2014
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