puzzle

The state of feeling confused or mystified because one cannot understand a complicated matter, a problem, etc.; bewilderment, confusion; (countable) often in in a puzzle: an instance of this.

A thing such as a complicated matter or a problem which is difficult to make sense of or understand; also, a person who is difficult to make sense of or understand; an enigma.

Often preceded by a descriptive word: a game or toy, or a problem, requiring some effort to complete or work out, which is intended as a pastime and/or to test one's mental ability.

Short for puzzle-peg (“a piece of wood secured under a dog's jaw to keep the dog's nose away from the ground so that it uses the scent in the air to track its quarry, and to prevent the dog from tearing the quarry once found”).