What does "occult" mean?

Occult: Hidden from the eye or the understanding; inviable; secret; concealed; unknown. It is of an occult kind, and is so insensible in its advances as to escape observation. I. Taylor. Occult line (Geom.), a line drawn as a part of the construction of a figure or problem, but not to appear in the finished plan. -- Occult qualities, those qualities whose effects only were observed, but the nature and relations of whose productive agencies were undetermined; -- so called by the schoolmen. -- Occult sciences, those sciences of the Middle Ages which related to the supposed action or influence of occult qualities, or supernatural powers, as alchemy, magic, necromancy, and astrology.