Its when you place a hard penis on someones forehead. The balls will also be resting on their head. It resembles a unicorn. Placing a soft penis on someones head is baby unicorning. And if this takes place in a pool or water it is known as narwhaling.
During a party you find a passed out person and place your hard dick on their forehead, balls at the base of the forehead, this is known as unicorning.
A unicorn orgasm is like the greatest orgasm ever. Your body/parts of your body go numb. You have muscle spasms that last longer than the sex. It lasts longer than your average joe or orgasms and you don't think it'll ever stop. It's almost like you black out and go to a different world for that period of time. Sometimes you cry after. Your whole body is tense and relaxed at the same time. And you feel like a teenager again because you don't want to stop. It's. That. Good.
Go to a fast food place like maccas, order a soft serve cone then ask the person if the believe in unicorns and stick the cone on your forhead saying believe(best done in the drive thru)