WordNet (r) 3.0 (2006):

postfix notation
    n 1: a parenthesis-free notation for forming mathematical
         expressions in which each operator follows its operands
         [syn: postfix notation, suffix notation, reverse
         Polish notation]

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

postfix notation
postfix syntax
Reverse Polish Notation
reverse polish syntax
RPN

    (Or "Reverse Polish Notation", RPN) One of the
   possible orderings of functions and operands: in postfix
   notation the functions are preceded by all their operands.
   For example, what may normally be written as "1+2" becomes "1
   2 +".  Postfix notation is well suited for stack based
   architectures but modern compilers reduced this advantage
   considerably.

   The best-known language with postfix syntax is FORTH.  Some
   Hewlett-Packard calculators use it, e.g. HP-25, HP-29C,
   HP-41C, HP-23SII.

   Compare: infix notation, prefix notation.

   (2003-06-23)