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
You're so naturally retardable, playing the part of a mentally challenged person comes easily to you.
I'm sorry I keep screwing things up, I'm feeling quite retardable today.
That was very retardable of you to remember to flush the toilet, but forget to wipe.
"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.