Definitions of NLP
There is no one single definition of NLP broad enough to encapsulate the breadth and depth of the subject matter. NLP has as many definitions as there are people practicing it.
"The name of the field refers to (Neuro) the human nervous system, including the brain and the five senses, (Linguistic) the verbal and non-verbal languages with which we communicate and (Programming) the ability to structure our neurological and linguistic systems to achieve desired results" - Jamie Smart, Salad NLP.
NLP was discovered by watching theraputic experts doing what they did and modelling their behviour so that it could be taught to others to allow them to achieve the same results.
The best way to define NLP is to do it for yourself - to learn and practice the techniques handed down to us by the creators and developers of NLP and to measure by the results that you get exactly what NLP means for you.
Here's a few definitions that I've learned from the various books and audio materials that I've studied to get you started:-
"NLP is an explicit and powerful model of human experience and communication. Using the principles of NLP it is possible to describe any human activity in a detailed way that allows you to make many deep and lasting changes quickly and easily" - John O. Stevens (now better known as Steve Andreas) in the foreword of Frogs into PRINCES - Richard Bandler & John Grinder.
"It's an attitude that has to do with curiosity, with wanting to know about things, wanting to be able to influence things, and wanting to be able to influence them in a way that's worthwhile" - Richard Bandler in Using Your Brain For A Change.
"It's an attitude and a methodology that leaves behind a trail of techniques..." - Richard Bandler
"For me NLP is the psychology of achievement and inter-personal communication" - Chris Howard
"....an owners manual for the mind" - Chris Howard