A sexual act that involves a male recieving oral sex, and when sufficiently aroused the erect penis is then submerged into liquid nitrogen, partially or completely freezing it.
Have you seen the freezie blow video?
When the erect penis is submerged in liquid nitrogen, or has liquid nitrogen poured on it in order to experience pleasurable sensations from fast freezing. The cold penis will have the appearance of being covered with frost.
I have a container of liquid nitrogen to give myself a frosty boy tonight