Puzzle
/ˈpʌzəl/
noun
Anything that is difficult to understand or make sense of.
“Where he went after he left the house is a puzzle.”
A game for one or more people that is more or less difficult to work out or complete.
A crossword puzzle.
Synonyms: anybody's guess, anyone's guess, conundrum, enigma, mystery, crossword, crossword puzzle, brain-teaser
verb
To perplex (someone).
To think long and carefully, in bewilderment.
“We puzzled over the curious-shaped lock, but were unable to discover how the key should be inserted.”
To make intricate; to entangle.