To shrug off ones own responsibility in a situation or act. To let the weight,burden or blame of a wrong doing fall off of one's conscience by brushing the responsibility to some one else.
When John's boss was angry for his department's bad performance, he became Slippery Shouldered by explaining that company did not have the right equipment.
Most popular in prison these days, slippery thighs has become the act of repressed homosexual desires unleashed. the two partners make love to each others thighs while sticking the feet of one another in front of the others face, this is done with a great deal of spit and or sweat.