ur mom is a definition of a particular overweight/fat women with autistic children.
"ur mom is so fat she ate the hamburger sign"
a cow like human that gave birth a is so fat that is the heaviest animal on earth
person1: i like u
person2: ur mom fat
person1: thank you
A joke that isn't so funny but can be made into a rap
What's that thing in the back of the car? Ur Mom! Ur Mom! Ur Mom!