retronym

n. new word or term that distinguishes a secondary class from members of a superclass

A retronym is a type of neologism coined for an old object or concept whose original name has come to be used for something else, is no longer unique, or is otherwise inappropriate or misleading. The term was coined by Frank Mankiewicz [1] and popularized by William Safire [2] in 1980 in the New York Times. Many of these are created by advances in technology. However, a retronym itself is a neological word coinage consisting of the original noun with a different adjective added, which emphasises the distinction to be made from the original form.
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<jargon> A term invented to distinguish a subclass of things from new members of the superclass, where the distinction was previously not necessary, since the old subclass had been all there was of the superclass.
For example, the retronyms "snail mail" and "paper mail" were coined by those for who "mail" was likely to mean electronic mail.
While the English language in general has a few retronyms ("whole milk", "snow skiing", "acoustic guitar"), hacker jargon is necessarily (at points capriciously) rich in retronyms, e.g. plaintext, natural language, impact printer, eyeball search, biological virus.
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(2001-02-25)