A term referring to a particular kind of showy muscular physique that conveys a fallacious impression of physical strength or toughness with regard to its bearer; muscles that are "just for show."
Brandon Marshall: "(Joey Porter) is one of those guys who all of those muscles are popcorn muscles. He's soft."
Joey "Peezy" Porter: "Nope (I don't know what popcorn muscles are). I know Orville Redenbacher. I know popcorn."