In cryptography, a statistical distribution of characters matching what a human would produce while typing "random" keystrokes. Unlike a uniform distribution, certain characters and character combinations are much more likely than others; for example, the conditional probability of a character c2 given the previous character c1 is higher if c1 and c2 are adjacent on the keyboard and typed with the same hand.
The string asdfasdf is an example of a highly probable string in a typewriter random distribution for a U.S. or English keyboard.