A universal phrase that can be used in almost any situation. Usually in response to someone overreacting to something, or when someone does something bad.
"Jim: What the fuck are you doing?! Those are my chips!"
"Kevin: Dude. Don't be so mayo."
*Guy falls off of his skateboard*
"Guy watching: Dude. Don't be so mayo."
"Kevin: Dude. Don't be so mayo."
*Guy falls off of his skateboard*
"Guy watching: Dude. Don't be so mayo."
by Alcranky May 22, 2010
When someone fails at something, you refer to an achievement from skate 3 called Don't be so mayo which was sponsered by miracle whip.
by Oh gaom July 1, 2010