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.
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Example sentences from the Web for off guard
Although the blood-spattered offices will be off-limits, staff have vowed to continue producing the magazine.
A guard is manning the door, which is always kept ajar so she can be monitored.
A passing off-duty school safety officer named Fred Lucas said that he had been told the man was a drug dealer.
The NOPD fired Knight in 1973 for stealing lumber from a construction site as an off-duty cop.
The off-year special election into which Duke threw himself drew little media notice at first.
In particular the Governor of Adinskoy offered us a guard of fifty men to the next station, if we apprehended any danger.
A far-off volley rumbled over the plain, and a few birds stirred uneasily among the trees.The Red Year|Louis Tracy
On the evening of September 17th he sent away his advance guard of two thousand men in eighty small boats.Napoleon's Marshals|R. P. Dunn-Pattison
Leaving Bruno to guard, Harry climbed the tree, and to his satisfaction had a good view of the country.
Every precaution was taken by Colonel Guitar to guard against a night attack, but his little army was allowed to rest in peace.