off guard

Idioms  

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

But the accumulated costs over time can balloon to a sum that can catch budget-conscious seniors off guard.

From MarketWatch • Apr. 15, 2026

I loved when a dish caught me off guard.

From Salon • Mar. 17, 2026

"We were taken off guard that it seemed to be working on time scales similar to that of silicon photodetectors."

From Science Daily • Mar. 4, 2026

The timing and scale of the conflict might have caught many off guard, Ebury’s head of market strategy Matthew Ryan said in a note.

From The Wall Street Journal • Mar. 2, 2026

She had planned to be stern and unyielding in her demands, but the admiral’s compliments caught her off guard, as did his reference to poetry.

From "The Unseen Guest" by Maryrose Wood