One that is puzzling, ambiguous, or inexplicable.(noun)
A perplexing speech or text; a riddle.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "enigma" in a sentence
"Suffice it to say here that this triple enigma is as comforting as wine and open as an English fireside; that this thing that bewilders the intellect utterly quiets the heart: but out of the desert, from the dry places and, the dreadful suns, come the cruel children of the lonely God; the real Unitarians who with scimitar in hand have laid waste the world."
"Nathan Lee in the Voice: See Los Muertos with virgin eyes; this cool-headed enigma is best approached cold, ignorant of everything but the title."
"The C-value enigma is real, and there is a lot of research going on right now investigating it."