a short and esp humorous verbal puzzle

a mystifying phenomenon

the riddle of her disappearance

something or somebody difficult to understand

to speak in riddles

to explain or solve (a riddle)

to separate (e.g. grain from chaff) with a riddle; to sift

to pierce (something) with many holes

to spread through (something), esp as an affliction

The state … was riddled with poverty — Thomas Wood