1: the ability in which to resemble a retarded person in behavior by being limited in intellectual or emotional development---often taken to be offensive
2: the development or academic progress of retarding others
3: the act or instance the extent to which something may be affected with retardedness
"Retardable" (informal, slang, portmanteau):
A blend of "retarded" and "relatable"; used to describe a person, statement, or behavior that is foolish or absurd in a humorous way, yet oddly familiar or relatable.