When you have a boner at a
time when you dont want one, but for some
reason you just can't get rid of it as a result of subconscious sexual thoughts. When you try to distract yourself from sexual thoughts in order to
lose the boner, sexual hallucinations only worsen. As a result, the boner only stays longer and you have no power over it.
John: "
Man, I was in class today and I got this huge boner and all of a sudden, I could only think about sex! I hope no one saw it."
Fred: "Dude, that sounds like you had a
bad case of Subconscious Boner Syndrome!"