Both hypnosis and meditation have been around for a long time, probably since the dawn of humanity. There are cave drawings that depict priests in what are clearly tranced states. Sanskrit writings describe hypnotic states and how to enter them. The Native American vision quest involves self-hypnosis. At the same time, meditation is practiced in various forms around the world; and it is described in ancient Chinese and Hindu writings.
It is also true that both meditation and hypnosis involve altered states of consciousness, and both use well-defined techniques to achieve those altered states. Meditators repeat mantras, or repetitive movements. Hypnotists use such things as eye fixation and hand levitation.
Also, both hypnosis and meditation lead to a shift away from the beta brain waves that are found in a normal state of wakefulness. However, those brain waves differ in the two states.
In meditation, it is typically true that the brain, especially in the frontal lobes, is dominated by theta waves, which are a step slower than the alpha waves usually found in a relaxed but alert state. In hypnosis, the frequency of brain waves depends on the depth of the trance. In a light trance, where most hypnotic work is done, alpha waves are dominant. In a deeper trance, the kind you might use for past regression, theta waves are strongest. In the very deepest, somnambulistic trances, where the person has zero conscious awareness of what is going on, the very slowest frequency, the delta wave, is in control.
In addition, hypnosis and meditation have different impacts and different results. In meditation, the goal is to empty the mind, to have no thoughts, to lose awareness of any mental activity. Once you have accomplished that, your job is done. In hypnosis, the task is not to empty the mind, but to focus it as sharply as possible in order to accomplish a specific goal—stopping smoking, eliminating pain, resolving an emotional trauma, or sharpening a skill.
You could see hypnosis as being like having a spotlight turned on to light up some specific area in your mind, while meditation is a way to dim the light, or even turn it off. Meditation is a great tool for achieving a general sense of calm. Hypnosis is a goal-oriented tool for getting a specific job done.