When the thought of being with or performing a sexual action with a person is the equivalent of doing such things with your grandmother.
Person A: Brandon is cute. Why don't you go on a date with him?
Person B: Ew! No way! He's in the grandma zone. That's so gross.
Person B: Ew! No way! He's in the grandma zone. That's so gross.
by Kattywin August 26, 2014
Get the grandma zonemug.