occult: Something that is hidden, e.g. secret or reserved knowledge.
orb: A type of anomaly that appears in photographs, especially digital flash photography, in which mysterious objects appear floating in the air.
omen: An event interpreted as a prediction of a future event.
oracle: A method of divination through contact with spirits or gods.
Order of the Knights Templar: A military and religious order founded in Jerusalem during the Crusades.
Ouija Board: A board containing letters and numbers, used to make contact with spirits.
out of body experience: AKA astral travel or astral projection, the experience of leaving one's physical body and possibly travelling to a distant place.