Definition of "Riddle" :

noun: a coarse sieve (as for gravel)

noun: a difficult problem

verb: set a difficult problem or riddle

"Riddle me a riddle."

verb: explain a riddle

verb: speak in riddles

verb: spread or diffuse through

"His campaign was riddled with accusations and personal attacks."

verb: pierce with many holes

"The bullets riddled his body."

verb: separate with a riddle, as grain from chaff