Mysterious

Words that describe something that is difficult to understand.

• What words describe something that cannot be understood?
  not understandable inscrutable unfathomable incomprehensible inconceivable
• What words describe something that is difficult to understand?
  vague oblique unclear not well worded cryptic hard to understand difficult to understand puzzle puzzling riddle
• What words describe an unclear connection between two things?
  obscure shrouded in mystery mysterious