Big iron, as the hacker's dictionary the Jargon File defines it, "refers to large, expensive, ultra-fast computers. It is used generally for number crunching supercomputers such as Crays, but can include more conventional big commercial IBM mainframes".
The term is often used in reference to IBM mainframes, often when discussing their comeback/survival after the assault of lower cost Unix systems. More recently the term is also applied to powerful computer servers and computer ranches, whose steel racks naturally invoke the same association.
The expression may be compared with the slang expression for heavy handguns, derived from the slang "iron" for a handgun ("shooting iron"), as exemplified by the classic country music ballad Big Iron by Marty Robbins about "the ranger with the big iron on his hip".
Famous quotes containing the words big and/or iron:
“Telephone poles were matchsticks, put there to be snapped off at a whim. Dogs trotting across the road were suddenly big trucks. Old ladies turned into moving—vans. Everything was too bright, but very funny and made for my delight. And about half a mile from my long liquid breakfast I turned carefully down a side street and parked, and sat beaming happily through the tannic fog for about an hour, remembering how witty we all had been, how handsome and talented ... [ellipsis in original]”
—M.F.K. Fisher (1908–1992)
“We are told that every American boy has the chance of being president. I tell you that these little boys in the iron cages would sell their chance any day for good square meals and a chance to play.”
—Mother Jones (1830–1930)