noun

1. an optical illusion in which the image of a distant object, as a ship or an oasis, is made to appear nearby, floating in air, inverted, etc.: it is caused by the refraction of light rays from the object through layers of air having different densities as the result of unequal temperature distributions
2. something that falsely appears to be real

Etymology: Fr < (se) mirer, to be reflected < VL mirare, to look at, for L mirari: see miracle