Note: Unless otherwise noted, definitions are courtesy of dictionary.die.net, an Internet dictionary in the public domain.J
Juggernaut--originally, an embodiment of the Hindu god Vishnu; now, any unstoppable force (the author).
Jung, Carl--a psychoanalyst and a one-time follower of Sigmund Freud; Jung developed the theory of a racial, or “collective unconscious” in which archetypes are stored (the author).
Ketamine anesthetic--a dissociative anesthetic that may cause so-called near-death experiences (the author).
King, Stephen--a contemporary best-selling author of short stories, novels, and screenplays in the horror genre. He has also written non-fiction articles and books.
Kirlian photography--the photographing of objects which exhibit a halo, or aura, effect as a result of the images created on a photographic plate due to high-voltage electric fields, pressures, moisture, and other natural conditions (the author; The Skeptic’s Dictionary).
Lamarckian evolution--“A theory of biological evolution holding that species evolve by the inheritance of traits acquired or modified through the use or disuse of body parts” (“Lamarckism: Definition and Much More from Answers.com”).
Lamia--a monster capable of assuming a woman's form, who was said to devour human beings or suck their blood; a vampire; a sorceress; a witch.
Ley lines--“alignments of a number of places of geography interest, such as ancient megaliths” (Wikipedia).
Lie detector--a device that, by monitoring various physiological processes and conditions, such as blood pressure, heart rate, and muscle contractions, is said to be able to detect whether a person is telling the truth or lying; its results are not admissible as evidence in court proceedings and are controversial among scientists and other experts (the author).
Life after death (afterlife)--existence is some state that extends beyond the death of the physical body, as is a matter of faith in many religions (the author).
Lincoln, Abraham--16th president of the United States, whose term occurred during the American Civil War; Lincoln had a prophetic dream in which he foresaw his assassination, which followed several days later (the author)
Loch Ness monster--a sea-serpent-like animal, perhaps a plesiosaur, said to inhabit Scotland’s Loch Ness (the author).
Logical positivism--“a 20th century philosophical movement that holds characteristically that all meaningful statements are either analytic or conclusively verifiable or at least confirmable by observation and experiment and that metaphysical theories are therefore strictly meaningless —called also logical empiricism” (Merriam-Webster Online Dictionary).
Lucid dreaming--a dream during which the dreamer recognizes that he or she is asleep and dreaming and in which he or she may consciously interact with the dream images (the author).
Lycanthropy--in folklore, the magical ability of a person to assume the characteristics of a wolf; in medicine, a kind of erratic melancholy, in which the patient imagines himself a wolf, and imitates the actions of that animal.