From WordNet (r) 2.0 (August 2003) [wn]:
flummox
v : be a mystery or bewildering to; "This beats me!"; "Got me--I
don't know the answer!"; "a vexing problem"; "This
question really stuck me" [syn: perplex, vex,
stick, get, puzzle, mystify, baffle, beat,
pose, bewilder, stupefy, nonplus, gravel,
amaze, dumbfound]