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 operation

The 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
recursive

    When 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)