indiscreet
/ˌɪndɪˈskri:t; ˌɪndɪ`skrit/ adj
too open in what one says or does; lacking tact or caution 不稳重的; 不审慎的; 轻率的; 不策略的
Don't tell her any secrets; she's so indiscreet. 什麽秘密都不要告诉她, 她很不稳重.
One indiscreet remark at the wrong moment could ruin the whole plan. 若时机不当, 一言不慎, 可能毁掉整个计画.