From The Collaborative International Dictionary of English v.0.48 :
parser \pars"er\, n.
One who parses.
[1913 Webster]
From 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"
From 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)