Here some definitions of Hypnosis.
Hypnosis is a technique that takes you into the Hypnotic State, some times called trance, a state where you are able to access your subconscious mind more easily and accept suggestions more easily.
Hypnosis is an altered state of consciousness where the subconscious level of the mind is in a state of hyper-suggestibility.
Hypnosis refers to a state or condition in which the client becomes highly responsive to suggestions.