enigma
1. [ noun ] something that baffles understanding and cannot be explained
Synonyms: mystery closed_book secret
Examples:

"how it got out is a mystery" "it remains one of nature's secrets"

Related terms: perplexity perplex
2. [ noun ] a difficult problem
Synonyms: riddle brain-teaser conundrum
Related terms: problem riddle
Similar spelling:   Engman
  enigmatic
  Encinas
  Engen
  enzymatic
  engine