He had a way of throwing Helen off guard with his charm when she least expected it.

他有办法用他的魅力让海伦在最意想不到的时候失去戒备。

《柯林斯英汉双解大词典》

He escaped by passing himself off as a guard.

他伪装成看守人而得以脱逃。

《牛津词典》

A pickpocket needs targets who are relaxed and off guard.

扒手需要放松警惕的目标。

youdao

In a more conventional offense, the point guard is called upon to beat his man off the dribble in a one-on-one (or isolation) situation and penetrate to the basket for a pass or a shot.

FORBES: With Knicks Coach Mike D'Antoni Gone, Jeremy Lin Should Be Afraid. Very Afraid.