Mirage

[mi-rahzh] /mɪˈrɑʒ/

noun
1.
an optical phenomenon, especially in the desert or at sea, by which the image of some object appears displaced above, below, or to one side of its true position as a result of spatial variations of the index of refraction of air.
2.
something illusory, without substance or reality.
3.
(initial capital letter) Military. any of a series of supersonic, delta-wing, multirole French fighter-bombers.
/mɪˈrɑːʒ/
noun
1.
an image of a distant object or sheet of water, often inverted or distorted, caused by atmospheric refraction by hot air
2.
something illusory
n.

“optical illusion of water in sandy deserts,” 1812, from French mirage, from se mirer “to be reflected,” from Latin mirare (see mirror). Or the French word is from Latin mirus “wonderful” (see miracle).
mirage
(mĭ-räzh’)

An image formed under certain atmospheric conditions, in which objects appear to be reflected or displaced or in which nonexistent objects seem to appear. For example, the difference in the index of refraction between a low layer of very hot air and a higher level of cold air can cause light rays, travelling down from an object (such as the sky or a cloud) and passing through ever warmer air, to be refracted back up again. An observer viewing these light rays perceives them coming up off the ground, and thus sees the inverted image of the object, which appears lower than the object really is. In this way the sky itself can be reflected, resulting in the mirage of a distant lake.