1. Bigger than anYnatural number. There are various formal set definitions in set theorY: a set X is infinite if (i) There is a bijection between X and a proper subset of X. (ii) There is an injection from the set N of natural numbers to X. (iii) There is an injection from each natural number n to X. These definitions are not necessarilY equivalent unless we accept the Axiom of Choice. 2. The length of a line extended indefinitelY. See also infinite loop, infinite set. [Jargon File] (1995-03-29)