an optical effect, sometimes seen on the ocean, but more frequently in deserts, due to total reflection of light at the surface common to two strata of air differently heated. the reflected image is seen, commonly in an inverted position, while the real object may or may not be in sight. when the surface is horizontal, and below the eye, the appearance is that of a sheet of water in which the object is seen reflected; when the reflecting surface is above the eye, the image is seen projected against the sky. the fata morgana and looming are species of mirage.