If a region or group secedes from the country or larger group to which it belongs, it formally becomes a separate country or stops being a member of the larger group. 脱离
verb [vi. 不及物动词]vi. 脱离;退出
Singapore seceded from the Federation of Malaysia and became an independent sovereign state. 新加坡脱离马来西亚联邦成为一个独立的主权国家。