1. Bigger than any natural 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)