(n.) a staircase that spirals round, with turning steps.
Idiom to describe a situation where the next step is not always clear, and a large amount of training in doing this is required.
This project has become something of a spiral staircase.
Is a sexual position in which the male enters the female from behind, pushes her face into the pillow and then sticks his thumb into her ass and twists in a clockwise motion. This gives the sensation of the downward forcing motion during thrusts from the pelvis.
Hey man, I took this girl home lastnight and gave her the spiral staircase!