The Free On-line Dictionary of Computing (30 December 2018):

travelling salesman problem
travelling salesman
TSP

    (TSP or "shortest path", US:
   "traveling") Given a set of towns and the distances between
   them, determine the shortest path starting from a given town,
   passing through all the other towns and returning to the first
   town.

   This is a famous problem with a variety of solutions of
   varying complexity and efficiency.  The simplest solution (the
   brute force approach) generates all possible routes and
   takes the shortest.  This becomes impractical as the number of
   towns, N, increases since the number of possible routes is
   !(N-1).  A more intelligent algorithm (similar to iterative
   deepening) considers the shortest path to each town which can
   be reached in one hop, then two hops, and so on until all
   towns have been visited.  At each stage the algorithm
   maintains a "frontier" of reachable towns along with the
   shortest route to each.  It then expands this frontier by one
   hop each time.

   Pablo Moscato's TSP bibliography
   (http://densis.fee.unicamp.br/~moscato/TSPBIB_home.html).
   Fractals and the TSP
   (http://ing.unlp.edu.ar/cetad/mos/FRACTAL_TSP_home.html).

   (1998-03-24)