不便 (bù biàn) means 'inconvenient' (opposite of 方便) or 'inappropriate/unsuitable' (similar to 不宜 'not advisable' and 不当 'improper'). As 'inconvenient', it focuses on lack of convenience, not on causing trouble (麻烦). As 'inappropriate', it often describes socially awkward situations, while 不宜 advises against actions and 不当 criticizes improper behavior. It also appears in the fixed phrase 手头不便, meaning 'short of cash'.