flaw, n. 1. an imperfection or weakness; Middle English flake, akin to Old English floh "flat stone," 1586. 2. in gamerese, a character attribute or stat designed to give recognizable or exploitable weakness or defect, often in exchange for merits. Ex: Player: "Okay, I'm going to take the two-point flaw Left-Handed, which gives me two merit points. Then I'll take the one-point merit Ambidextrous, and use the extra point towards Razor Claws." GM: "Um, no." See disad. [GJ1]
Addendum: Flaws are most popularly used in WoD games, and as the example shows, can often be horrendously abused.