Not to be confused with the Danza Slap or Turkeyslapping, the purple shamrock is when a man slaps a woman across both sides of her face with his penis, immediately after receiving oral sex. In some cultures, it is a demonstration of respect and admiration.
As Sheila knelt on the floor, Raul showed his gratitude for the finest blowjob of his life, by bestowing upon her the Purple Shamrock.
When, on St. Patrick's day (or night), a guy living or staying in Cambridge blows his load on his girl, preferably her face, while simultaneously flinging a handful of bright green glitter at her so it sticks to the jizz.
Yeah, we fucked for a bit, but when she asked me to turn off the Dropkick Murphys playing in the background I had to give her a Cambridge shamrock.