- A heavy drinker; an alcoholic.
- One who regularly uses a steroid or other substance designed to enhance athletic performance.
May be a mildly pejorative term, but not so when used as a term of endearment or by those partaking, especially amongst themselves.
From juice + -head. Juice is a reference to protein shakes, anabolic steroids, and other performance enhancing drugs, many of which are taken in liquid form and called juice by analogy.