flummox
1. [ verb ] be a mystery or bewildering to
Synonyms: puzzle bewilder baffle mystify amaze stick stupify stupefy gravel nonplus get dumbfound pose trounce beat vex perplex
Examples:

"This beats me!" "Got me--I don't know the answer!" "a vexing problem" "This question really stuck me"

Related terms: confuse stagger elude riddle stump solve puzzle_over mystery bewilderment mystification mystification stupefaction puzzle