indiscreet
adj
too open in what one says or does; lacking tact or caution 不穩重的; 不審慎的; 輕率的; 不策略的
Don't tell her any secrets; she's so indiscreet. 什麼秘密都不要告訴她, 她很不穩重.
One indiscreet remark at the wrong moment could ruin the whole plan. 若時機不當, 一言不慎, 可能毀掉整個計畫.