Conundrum (noun)
kon-un-drum
A confusing and difficult problem, question or riddle.
Late 16th century of unknown origin, but first recorded in a work by Thomas Nashe, as a term of abuse for a crank or pedant, later coming to denote a whim or fancy, also a pun. Current senses date from the late 17th century.
Example sentences
“It was quite the conundrum for them to solve.”