Adjective: Used in the same manner as many people use "retarded", it refers to a situation, person, or thing that is ill-equipped for life due to an obvious defect.

It is derived from the hypothetical situation in which Frank Sinatra has an affair with his own daughter, Nancy, and they bestow their new inbred love child with the moniker "Nank," a portmanteau of their own names.

This is preferred over "retarded" or "gay" because of its low level of offense to various groups of people (i.e., individuals who actually are mentally challenged or gay). Frank and Nancy might not prefer it, but that's what they get for engaging in fictional incest.