The act of purchasing an ice-cream cone at a drive through, asking the person if they believe in unicorns, then sticking the ice-cream cone to your forehead while slowly driving away screaming, "believe"!!
Mary and Jane went uniconing through the drive-through window with icecream cones stuck to their forheads.
The act of purchasing an ice cream cone, asking the man/woman at the drive through window if they believe in unicorns, and after their response you immediately smash the ice cream cone on your forehead screaming "Believe!!!!!"
Amy and Sandra went uni-coning at mcdonalds, getting ice cream all over their faces!