a set of useless, bullshit rules that girls use to govern and bully around their friends, girls or guys.
examples of breaking the girl code:
1. you slept with a guy a friend used to like
2. you ask a guy out that you once saw an aquaintance out with a month before
3. you are friends with someone your friend hates
Girl 1: "what did i do wrong?"
Girl 2: "hello!? you fucking broke the girl code rule #27."
Girl 3: "oh, duh, i checked out a guy that you once that was cute. i am so sorry."