WordWeb Online

1. Lacking clarity of meaning; causing confusion or perplexity
   "perplexing to someone who knew nothing about it";
   - confusing, puzzling

1. Be confusing or perplexing to; cause to be unable to think clearly
   "These questions perplex even the experts";
   - confuse, throw, fox, befuddle, fuddle, bedevil, confound, discombobulate, vex, stick, get, puzzle, mystify, baffle, beat, pose, bewilder, flummox, stupefy, nonplus, gravel, dumbfound
    
2. Make more complicated
   "There was a new development that perplexed the matter";
   - complicate

See also: muddy, unclear

Type of: alter, be, change, modify