The Collaborative International Dictionary of English v.0.48:

parser \pars"er\, n.
   One who parses.
   [1913 Webster]

WordNet (r) 3.0 (2006):

parser
    n 1: a computer program that divides code up into functional
         components; "compilers must parse source code in order to
         translate it into object code"

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

parser
parse
parsed
parsing

    An algorithm or program to determine the
   syntactic structure of ("to parse") a sentence or string of
   symbols in some language.  A parser normally takes as input
   a sequence of tokens output by a lexical analyser.  It may
   produce some kind of abstract syntax tree as output.  A
   parser may be produced automatically from a grammar by a
   parser generator such as yacc.

   A parser is normally part of some larger program, like a
   compiler, which takes the output of the parser and attempts
   to extract meaning from it in some way, e.g. translating it
   into another language.

   (2009-06-26)