In hypnosis, the term ‘susceptibility’ means how easily a person can be hypnotized.
How easily to be hypnotized has to do with our consciousness/ movement. As it is known that we move in and out of our consciousness on a constant basis. Some people stay in a consciousness longer while some move in and out easily.
A person who has no difficulty getting to a state of drowsiness / mind tune out of conscious activity can enter into a trance or hypnosis fast.