noun, disease affecting a person or an animal in a way were they cant stop thinking of crazy unicorns. this usually gets them in trouble but the person with the disease is most likely hardcore enabling them to squeeze out of tight situations. no cure discovered.

When you're being horny (especially around friends) and as a result shame ensues.

Unicorn Head means that a girl/guy is dressed as a unicorn while giving head so hard that the guys genitals start to turn different colors like a rainbow