1. (mathematics) an expression such that each term is generated by repeating a particular mathematical operation;

The Collaborative International Dictionary of English v.0.48:

Recursion \Re*cur"sion\ (-sh?n), n. [L. recursio. See Recur.] The act of recurring; return. [Obs.] --Boyle. [1913 Webster]WordNet (r) 3.0 (2006):

recursion n 1: (mathematics) an expression such that each term is generated by repeating a particular mathematical operationThe Jargon File (version 4.4.7, 29 Dec 2003):

recursion n. See recursion. See also tail recursion.The Free On-line Dictionary of Computing (30 December 2018):

recursion mutually recursive mutual recursion recurse recursiveWhen a function (or procedure) calls itself. Such a function is called "recursive". If the call is via one or more other functions then this group of functions are called "mutually recursive". If a function will always call itself, however it is called, then it will never terminate. Usually however, it first performs some test on its arguments to check for a "base case" - a condition under which it can return a value without calling itself. The canonical example of a recursive function is factorial: factorial 0 = 1 factorial n = n * factorial (n-1) Functional programming languages rely heavily on recursion, using it where a procedural language would use iteration. See also recursion, recursive definition, tail recursion. [Jargon File] (1996-05-11)