A shape whose pattern repeats at every scale. The whole is in each part, which is why zooming reveals no new kind of thing.
Coined in 1975 by mathematician Benoit Mandelbrot from Latin fractus (broken, fractured), past participle of frangere (to break); a shape whose pattern repeats at every scale it is broken into.
Zooming in should eventually show something new, and this is the exception: the pattern found at any distance is the same pattern found at every other, so scale stops being informative.