I cam across this definition of NLP from Philip H. Faber:
“There is more to our thought, behavior and communication than normally meets the eye, ear, or hand. With roots in General Semantics, Transformational Grammar, and Ericksonian Hypnosis, Neuro-Linguistic Programming (NLP) delves into the conscious and unconscious patterns that lie beneath the maps and models of our subjective experience. An understanding of how we create our mental maps allows a wider range of conscious choices – and the results include the ability to change behavior quickly and effectively, heightened powers of communication and persuasion, and a key to exploring and re-creating altered states of consciousness. Once only in the province of therapists, NLP has proved itself useful to teachers, salespeople, managers, body-workers, writers, artists, parents, explorers of consciousness, and just about everybody else!”
It is probably the simplest and best definitions of NLP I have seen.