something that baffles understanding and cannot be explained
"how it got out is a mystery"
"it remains one of nature's secrets"
a difficult problem
"The missing funds remain an enigma that has baffled every accountant who has reviewed the ledger."
Something or someone puzzling, mysterious or inexplicable.
"The sudden disappearance of the entire village left the search team baffled by an enigma that defied all logical explanation."
A German device used during World War II to encode strategic messages.
"The intelligence team worked around the clock trying to crack the Enigma, the German machine that had kept their communications secure throughout the war."