To compromise, sabotage, or interfere with ones 'game'. Game in this context refers typically to scoring, as in sex or in a sport but it could refer to any activity.

It probably derives from salting the earth to prevent growth.
"Step off when I'm making my move or you'll salt my game."

"Don't do it while you're nervous or it will salt your game."
by Eater of Kittens February 2, 2009
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