Answer: enigma

AnswerCrossword Clue
ENIGMAPuzzling situation
ENIGMAWorld War II encoding machine
ENIGMABrainteaser
ENIGMAPuzzler
ENIGMAIt's puzzling
ENIGMASomething of a mystery
ENIGMAIt's something of a mystery
ENIGMAMona Lisa's smile, for one
ENIGMAInscrutable sort
ENIGMAIt's hard to understand
ENIGMAPuzzling person
ENIGMARiddle relative
ENIGMASomething hard to grasp
ENIGMABrain twister
ENIGMAPuzzlement
ENIGMAHead-scratcher
ENIGMA" .. Variations": Elgar opus
ENIGMAPerplexing puzzle
ENIGMAIt's a mystery
ENIGMAPerplexity
enigmasomething that is difficult to understand
ENIGMAMystery
ENIGMARiddle
ENIGMAPuzzle
ENIGMA"Hmmmmmm" provoker
ENIGMAReal poser
ENIGMAStumper
ENIGMASomething inscrutable
ENIGMABaffler
ENIGMAPoser
ENIGMATough nut to crack
ENIGMA"Hmmmmmm" provokeer
ENIGMAEncryption machine of yore
ENIGMAWWII cipher machine
ENIGMAWWII coding machine
ENIGMAChallenging riddle
ENIGMAConundrum
ENIGMAToughie
ENIGMAProblem
ENIGMABaffling problem