Typically a penis small in size, dirty in nature. The pubic region is usually matted with a moldly substance or a flakey crust. A common symptom is a greasy like secretion found on ones under garments or the penis tip. Medically referred to as a Gustavo Alonso.
Man, last night I was at the club and this guy was grinding his Fungus Stick on me, damnit I got Gussed again.