The phrase "off guard" means to be caught unaware and unprepared. There are several synonyms for the word "off guard" which can be used in different contexts. One such synonym is "unawares," which implies being taken by surprise suddenly. Another synonym is "defenseless," which means without any means to protect oneself. "Unprepared" means not being ready for something that has happened unexpectedly. "Caught off balance" means being taken aback by an unexpected turn of events. Similarly, "surprised" and "startled" signify being shocked by unexpected developments. In essence, these synonyms serve as interchangeable alternatives to the phrase "off guard," but with slightly different meanings based on their context.