unobtainium n.

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’.

unobtainium, n. A substance having the exact high test properties required for a piece of hardware or other item of use, but not obtainable either because it theoretically cannot exist or because technology is insufficiently advanced to produce it. Humorous or ironical.

None of the other moons in the Kthsemenee system had the one attribute this one possessed: a core of almost one percent unobtainium. Already thirty of the Brothers' ships had landed, to begin construction of the Weapon.

The place was swarming with day-glo lycra-clad riders and zillion-dollar unobtanium wonder bikes.

On Selfridge’s desk is a magnetic base, and hovering in mid-air, in the invisible field, is a lump of METALLIC ROCK. Pure UNOBTANIUM. He grabs it and holds it up between thumb and forefinger, in front of Grace’s eyes. Selfridge This is why we're here. Unobtanium. Because this little gray rock sells for twenty million a kilo.