1) When one, giving a blowjob, twists there head in a clockwise or counterclockwise direction while slightly twisting the penis in the opposite direction (can be done during the up and/or down stroke or both).
2) To give a blowjob in a repeated spiral fashion.
*Slurping is preferred but optional!
Also see: Cockswirl, Candycane, Tilt-a-Swirl
Whether it's for go or for show, she's a pro if she knows the Dick Twizzler!