Catch off guard is a phrase that describes the act of surprising someone, usually by doing something unexpected. The two crossword solutions for this phrase are 'STARTLE' and 'STUN', both of which refer to the act of shocking or surprising someone. STARTLE is a 7-letter word meaning to surprise or shock someone suddenly, while STUN is a 4-letter word meaning to cause someone to become motionless or speechless due to surprise or shock.