IQ ραδικιού -> room-temperature IQ, room temperature IQ, room temperature I.Q., room-temperature I.Q., dumb and dumber in one, dead slow, dead stupid, dumb, motorhead, complete and utter idiot, imbecile, dur-brain, numbnuts, numbskull, dimwit, dolt, blockhead, dumbbell, dumbo, slow on the uptake, dumber than a box of rocks, lamebrain, underhead, dunderhead

[spiros]

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IQ ραδικιού -> dead slow, dead stupid, dumb

[crystal]

dumb and dumber in one person, dumb and dumberer in one

[dominotheory]

motorhead

1: A car or motorcycle enthusiast. (1974 —) .
2: An idiot, fool. (1979 —) .
Record (Bergen County, New Jersey) Two motorheads named Beavis and Butt-Head who play 'ball' with a live frog, bludgeon a poodle and hum heavy metal tunes (1992).
http://www.answers.com/topic/motorhead-slang-term