Extreme standing up. Standing up straight with your hands at your side like a fence post. Basically it is the opposite of "planking" which is sometimes known as "extreme lying down."
The man is flat on his back and the women straddles him and rides him up and down, up and down... Preferably facingforward, the women is riding / posting him.
Stands for "Pretty Obvious Sexual Tension Involving Nasty Girl". "Nasty" can also mean Nice, New, Nefarious, or Neat. "Girl" can also be subbed for Guy. When, during a social encounter, there's a clear mutual attraction and desire for sexual intimacy that is never consummated.
"Dude, I should be banging right now because I was straight POSTING at that party"
A traditional execution method where a person is lifted onto a sharp stake in the ground and impaled rectally. The body weight slowly causes the person to be further impaled until a vital organ is reached, causing death.