an abbreviation of the phrase "just chillin, you?" in which scums, often a male, use in order to type faster to each girl they talk to.
scumbag: "hey"
girl 1: "hey whats up? :)"
scumbag: "jcu"
girl 1"samee."
scumbag: hey
girl 2: hiiii. what are you up too?
scumbag: jcu
3👍 2👎