One who riddles or sieves (grain, sand, etc.). A puzzler; one who asks riddles.

What is the meaning of Riddler?

noun One who speaks in riddles or enigmatically. noun One who works with a riddle or sieve.

Is the Riddler a killer?

The Riddler is a serial killer who is obsessed with both riddles and with learning the answer to the "ultimate riddle": the identity of the Batman.