Aside from the obvious defenitions regarding semen of some sort, this term can also be used to describe a slight misty rain; also known as drizzle. This term is especially appropriate when in the company of close friends while at the same time experiencing the rain for the first time in the day.
a: "Aw man, what the heck? It's raining now!"
b: "No dude, it's all good. It's just a slight jizzle."