Frequently Asked Questions About the GRE
Unlike on the SAT, there is no penalty for incorrect answers on the GRE. So you won't be penalized for guessing, exactly.
But because the test is adaptive, incorrect answers will determine what the next questions you receive are.
Which is why we don't advocate randomness in your guessing.
You're much better off if you can make educated guesses, if you can narrow the choices down some.
Your chances of hitting the right answer improve substantially if you can eliminate even one or two of the possible answers.