(abbrev. rv), stochastic variable, or chance variable, n. (Statistics) 1. a quantity that may take any of a range of values (either continuous or discrete) that cannot be predicted with certainty but only described probabilistically. The relative frequency with which the random variable takes a given value or lies in a given interval is the (empirical) probability of that value or interval. 2. formally, a measurable function defined on a probability space and having range in the interval [0, 1].