unobtainiumn.
/(ˌ)ʌnəbˈteɪnɪəm/, U.S. /ˌənəbˈteɪniəm/ colloquial (frequently humorous or ironic).
A hypothetical substance that would be highly desirable but is unrealized or unobtainable; a notional substance with exceptional or ideal properties.
ΘΚΠ
the world > existence and causation > existence > substantiality or concreteness > unsubstantiality or abstractness > [noun] > unsubstantiality or lack of substance > something lacking substance > a thing existing in name only
nominala1625
titulado1659
nominality1842
nominis umbrac1874
unobtainium1956
1956 Marshall (Michigan) Evening Chron. 27 Feb. 6/8 Scientists are now working on a new metal to be used in making the noses on intercontinental ballistics missiles. The metal is so hard to come by that the scientists have devised a lugubriously-humorous name for it. They call it ‘unobtainium’.
1958 Metal Progress Oct. 96/1 We need a metal with high melting point, excellent strength and ductility, but with near zero density. Such an element might be called ‘Unobtainium’; it does not exist.
1992 Bicycling May 4/1 (advt.) The place was swarming with day-glo lycra-clad riders and zillion-dollar unobtanium wonder bikes.
2008 Guardian 30 Aug. (Weekend Suppl.) 77/1 You can buy a basic Wii from any old Woolworths, but the Wii-Fit add-on is still made, as the saying has it, from purest unobtainium.
2010 New Yorker 4 Jan. 76/2 The Na'vi's turf is also rich with an energy-yielding mineral called Unobtainium (which is as close as Cameron comes to a joke in this movie).
This is a new entry (OED Third Edition, December 2014; most recently modified version published online December 2021).
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n.1956