The Webster's Dictionary definition of "meditate" This is the definition the Bible translators meant when they used the word "meditate."
Some Catholics also say it is "contemplative" exercise. This adjective's noun is "contemplation." These words are not in the Bible, but they are synonyms of "meditation."
Unfortunately, occultists are redefining these words to mean self-hypnosis through endless repetition of some word until it loses meaning, opening your natural barrier of integrity. This opens the door to spirits, also known as demons. They will then draw their human hosts to further infestation by other demons. Their goal is complete bondage of the human. This is the essential basis of Eastern, Animist and Shamanist religions. I've cast demons out of occultists when they got a bigger demon than they had bargained for.
True Christian Meditation is thinking through the implications and applications of the word of God in our lives. It is thinking through the concepts using sentences and paragraphs. Aspergers can also think in pictures.
Christian meditation can change to prayer if we change to speaking or dialoguing with God the Holy Spirit who dwells in our inner beings. This can be done by sentences, visions or a conscious inner knowing. Jesus Christ of Nazareth did this regularly to keep his attitude of love and dependence on God our Father a priority.