Iatrogenic - 
Refers to neurotic problems caused in patients unintentially during consultation, by words (badly phrased suggestions for example) or actions.
Ideomotor Response - 
Literally a physical response to an idea. Used in hypnosis for signaling. Typically the index fingers of each hand are designated 'yes' and 'no' values and the control of these fingers is passed to the hypnotized patient's subconscious mind, which then responds to questions by moving the 'Yes' or 'No' finger.
Implosion Therapy -
Also known as flooding, a practice originating with behaviour therapy. The patient is exposed to the source of anxiety (for example) without aversive consequences, until the fear eventually subsides.
Impotence -
Sexual impotence is the inability of the male to have an erection. Where this problem has a psychological origin it can be treated successfully with hypnosis.
Indirect Suggestions -
Also known as permissive suggestion. Referres to the phrasing of suggestions in such a way as to seem to give a choice to the patient as to how he reacts. Special attention is given to the placing of stress on certain words. For example "...If in a few moments time you would find a particular sensation in some part of your body, that would be good, a pleasant sensation, perhaps a gentle warmth or a feeling of relaxed heaviness..." Here it is indirectly suggested that the patient will find an internal sensation that will be either gentle warmth or relaxed heaviness, or perhaps both. As opposed to Direct (Authoritarian) Suggestion.
Induction -
Hypnotic induction describes the process used in the transition of the subject from normal waking consciousness into the 'hypnotic state'.
Insomnia - 
Sleeplessness, usually due to psychological reasons (stress/anxiety/repressed emotion). Responds well to treatment by hypnotherapy.
Introvert -
A term originally coined by C.G.Jung which has passed into popular parlance to
describe an inwardly focused personality type. As opposed to Extrovert.