1. (noun) something that baffles understanding and cannot be explained

• closed book
• mystery
• secret

2. (noun) a difficult problem

• brain-teaser
• conundrum
• riddle

1. (noun) something that baffles understanding and cannot be explained

• perplexity

2. (noun) a difficult problem

• problem

1. (noun) something that baffles understanding and cannot be explained

• amaze
• baffle
• beat
• bewilder
• dumbfound
• flummox
• get
• gravel
• mystify
• nonplus
• perplex
• pose
• puzzle
• stick
• stupefy
• vex
• cryptic
• cryptical
• deep
• inscrutable
• mysterious
• mystifying
• enigmatic
• oracular
• enigmatic
• enigmatic
• enigmatical
• enigmatical
• puzzling
• puzzling
• mysterious
• mystic
• mystical
• occult
• orphic
• secret
• mystify

2. (noun) a difficult problem

• riddle
• riddle