Answer: brainteaser

AnswerCrossword Clue
BRAINTEASERChallenging puzzle
BRAINTEASER"If three hens lay three eggs in three days ...," e.g.
BRAINTEASERIt may call for lateral thinking
BRAINTEASERPoser
BRAINTEASERHard puzzle
BRAINTEASERLingerie shown during a preview?
BRAINTEASERMental challenge
BRAINTEASERKnot
BRAINTEASERRiddle
BRAINTEASERDifficult puzzle
brainteasersomething (as a puzzle) that demands mental effort and acuity for its solution