Occult
OCCULT', adjective [Latin occultus, occulo; ob and celo, to conceal.]
Hidden from the eye or understanding; invisible; secret; unknown; undiscovered; undetected; as the occult qualities of matter.
The occult sciences are magic, necromancy, etc.
OCCULT lines, in geometry, are such as are drawn with the compasses or a pencil, and are scarcely visible.