A unicorn with a clarinet as a horn. one can be a clarineticorn by placing the bell of one's clarinet on their forehead and holding it there so that the rest of the clarinet sticks up like the horn of a unicorn. (usually done while running and/or making akward, loud noises)
Person 1: (running with their clarinet on their head) "AAAHH!!!"
Person 2: "dude, what's that guy doing"
Person 3: "oh he's just being a clarineticorn"