A neologism created for an existing object or concept because the exact meaning of the original term used for it has become ambiguous (usually as a result of a new development, technological advance, etc.).A retronym typically consists of the original term combined with a modifying word.
1980 W. Safire in N.Y. Times Mag. 27 July 8/1 Frank Mankiewicz, president of National Public Radio, collects these terms and calls them ‘retronyms’—nouns that have taken an adjective to stay up-to-date and to fend off newer terms. Other retronyms include ‘hard-cover book’.
1988 Washington Post (Electronic ed.) 6 Nov. g1 True art lay elsewhere, probably in what we now, in a classic retronym, call ‘live drama’.
1995 I. L. Allen City in Slang ix. 229 The name East Village was given..to borrow prestige from the name of Greenwich Village or just The Village, which then became known..by the retronym West Village.
2003 Edmonton (Alberta) Jrnl. (Nexis) 22 Nov. a13 Older folks, who actually grew up when all clocks had moving hands, phones had dials and wires, and milk was just plain old milk, are usually familiar with both the item and its retronym (analogue clock, rotary and land-line phones and whole milk).