The extreme form of the verb fruck. A headfruck is to meet the love of your life only to find out that your closest, bestest friend does not approve. A truly painful experience that may well lead to either losing your best friend or giving up the love of your life. Such a result is known as a complete headfruck.
"What's wrong with Peter he looks so miserable?"
"He's fallen head over heels in love with a real babe, but now John is pissed off with him cos he doesnt hang out as much as he used to. He's caught in a complete headfruck"