When a girl makes very noticeable changes to her appearance (ex. dying or cutting her hair, wearing particularly sexy clothes) before meeting up with her ex-boyfriend - who is usually the one who left her - a short period of time after the break up to "grab a coffee" or "get her stuff back". This is supposed to have the effect of a shock for the guy, who feels like he's already missed out on a lot and like she's doing great and moving on without him. The goal is to make him ultimately regret his decision.
We were supposed to go to a cafe today to "talk about it", but I bailed because I want Sarah to dye my hair before the next time he sees me, so that the Ex-Girlfriend Effect is be complete.