The Rice University Neologisms Database

Characterized by properties of something slow, challenged or stupid Clearly, the meaning is: characterized by the properties of a retard, or one who is mentally challenged; stupid, but in a slow, low-IQ sort of way (not offensive, slang-like). The root RETARD is commonly used to refer to something stupid, or slightly worse than stupid (like something uttered by a stupid or slow person), and the morpheme “ICAL” glosses adjectivally. Retarded was an apt adjective, and RETARDICAL was both a) funnier and b) better modelled after a statement made, rather than to refer to anything that can be referred to as retarded (generally a person). Possible models include RADICAL (for sounding purposes), ADJECTIVAL (for the ‘AL’ – morpheme that glosses an adjective).