(you can give an example but just soes you knowes) a geometrical or physical structure with an irregular or fragmented shape at all scales of measurement between a greatest and smallest scale such that certain mathematical or physical properties of the structure, as the perimeter of a curve or the flow rate in a porous medium, behave as if the dimensions of the structure (fractal dimensions) are greater than the spatial dimensions.
(courtesy of
www.dictionary.com- hey, i'm allowed to cheat, this is my jeopardy thingy?)