Used in situations where the word ridiculous or retarded is not enough to describe the fully mind blowing moronic action caused by a person/situation.
You leave your boss angry voice mails threatening to kill his puppies, drop a Cleavland Steamer on his desk and expect not to get fired. That's retardulous.
something that is so completely ridiculous on its face, that one must assume that the person who suggests or insists on it must be cognitively deficient to an incredible degree.
unpaid internships are retardulous. adjunct professorships are retardulous.