random walk

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A sequence of changes, either in the value of a random variable or in a process (as in the price of a share of stock), in which the direction and size of each change is randomly determined, subject to some specified rules.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun mathematics A stochastic path consisting of a series of sequential movements, the direction (and sometime length) of which is chosen at random

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a stochastic process consisting of a sequence of changes each of whose characteristics (as magnitude or direction) is determined by chance