WordNet (r) 3.0 (2006):

natural language processing
    n 1: the branch of information science that deals with natural
         language information [syn: natural language processing,
         NLP, human language technology]

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

natural language processing

    (NLP) Computer understanding,
   analysis, manipulation, and/or generation of natural
   language.

   This can refer to anything from fairly simple
   string-manipulation tasks like stemming, or building
   concordances of natural language texts, to higher-level
   AI-like tasks like processing user queries in natural
   language.

   (1997-09-12)