The act of taking a middleman or drug dealer taking a portion of the product for himself after receiving it from the next person up before selling it to customers, especially when this act is done covertly, IE among friends.
"Man that asshole said he split up the ounce he bought for us four ways, but I only got 5 grams, he skimmed the sack man!"
to skim traffic is to change a portion of links on a web page so that they don't direct to a destination originally suggested by their caption or image. This is done, for example, to divert some of the traffic on the TGPs to associated sites.
Setting skimming to 100, 80, 50 means first surfer's click will go to content (100% skim ratio), second will go to content with 80% probability, all others will go to content with 50% probability.