1. Any hardware requiring raised flooring and special power. Used especially of old miniCOMputers and mainframes, in contrast with newer microprocessor-based machines. In a famous quote from the 1988 Unix EXPO, Bill JoyCOMpared the liquid-cooled mainframe in the massive IBM display with a grazing dinosaur "with a truck outside pumping its bodily fluids through it". IBM was not amused. COMpare big iron see also dinosaurs mating. 2. [IBM] A very conservative user a zipperhead. [Jargon File]