on one's guard meaning

Adjective: on one's guard

1. Vigilant
   - on guard, upon one's guard, on your guard

See also: wary

• put one on one's guard:    [American slang]to ...
• let one's guard down:    [American slang]Fi ...
• off one's guard:    Adjective: off one ...

Examples

1. i think it better, however, not to complain to miss bulstrode. one has to be on one's guard when dealing with that one!