put your hand in a fist.
then move your wrist up and down.
you will see the muscle in your arm go up and down.
girls already have it but boys can develop a bigger jo muscle.
Type your email address below to get our free Urban Word of the Day every morning!
Emails are sent from email@example.com. We'll never spam you.
Log in with Facebook to save your favorite definitions
and share them with friends.