A mirage is the multiple imaging of objects near the horizon by atmospheric refraction in which erect and inverted images always alternate. However, some images are frequently so distorted as to be unrecognizable, leaving only a single recognizable inverted image or two erect ones. As with green flash phenomena, there are several kinds.
The term "mirage" should not be applied to displays of atmospheric refraction such as looming and towering that merely distort the ordinary erect image.