noun
enigma
ih-NIG-muh/ɪˈnɪɡmə/
Someone or something mysterious and difficult to understand.
The unopened stone puzzle remains an enigma with its hidden interlocking parts.

Etymology
Ainigma meant a dark saying or riddle. English broadened this idea from a statement concealing meaning to anything—or anyone—that an observer finds difficult to understand.
In context
con men the most devious of all criminals charming cool and calculating they betray trust and devastate lives yet remain a complete enigma we are about to explore the mysterious world of these master criminals
More examples
- The cause of her sudden departure remains an enigma.
- To his neighbors, the quiet inventor is an enigma.
- The ocean still holds many enigmas for scientists.
Forms
enigma · enigmas
enigmatic adjective — Mysterious and difficult to understand or interpret.