Did you mean mesomerism? It is a chemistry term. The property of some molecules of having a structure that cannot be represented by a single structural formula; resonance. (Source: http://en.wiktionary.org/wiki/mesomerism )
Mesmerism is essentially the same as hypnosis, the word mesmerism is just a lot older than hypnosis, and was packed with substantial misconceptions in the time it was used, which was the reason to change it.
You may have some misspellings in your question: Maybe it's Mesmerism, Hypnosis, as defined by the American Psychological Association Division of Psychological Hypnosis, is "a procedure during which a health professional or researcher suggests that a client, patient, or subject experience changes in sensations, perceptions, thoughts, or behavior." Any definition is necessarily vague, as the underlying mechanism is little understood. Some theories view hypnosis as an altered state of consciousness, others as a type of focused attention. Psychologists have recently researched hypnosis and found a strong correlation between the ease of putting someone in a state of 'hypnosis' and their level of suggestibility.