adj.措手不及的;没有提防的;无思想准备的;
例句:
The question caught her completely off-guard.
这个问题令她猝不及防。
The troops created a diversion and caught the enemy off guard.
军队声东击西,把敌军调离岗位.
Beware of the quiet ones; they always catch you off guard.
当心那些少言寡语的人, 他们往往会乘你不备,出奇不意.