off guard

1. Also, off one's guard. Not watchful, easily surprised. It is often put as catch (or be caught) off guard, meaning “take (or be taken) by surprise.” For example, The securities analyst was caught off guard by that financial report, or With any luck the boss will be off guard when I come in late. [Late 1600s] The antonym, on guard or on one's guard, meaning “watchful or prepared, especially to defend oneself,” was first recorded in 1577. For example, In this crowd we must be on guard against pickpockets, or I'm always on my guard when I'm asked how I voted.

Example Sentences

In the opening moments, a shooter springs upon authorities surveying a crime scene with almost supernatural speed, catching not just the police but also the audience off guard.

From Los Angeles Times

“We have been so used to making shots and so I think it caught us off guard a little bit,” Roberts said.

From Los Angeles Times

Hogan seemed caught off guard, and after plugging his new beer, went backstage.

From Los Angeles Times

When she first discovered her interviews were attracting attention, however, it caught her off guard.

From BBC

Authorities say many of the victims were caught off guard as water overtook low-lying areas with little warning.

From Salon