occult

To cover or hide from view.

The Earth occults the Moon during a lunar eclipse.

To dissimulate, conceal, or obfuscate.

[…]to do so would occult rather than illuminate the utterly unexpected and surprising character of his coming and of his reign.

Secret; hidden from general knowledge; undetected.

occult blood loss; occult cancer

This counter-influence is so much more conclusive[…] because it is of an occult kind, and is so insensible in its advances as to escape observation.

not visible, but chemically detectable.

occult blood in the urine

Related to the occult; pertaining to mysticism, magic, or astrology.

The concoctions contrived by Italians were particularly in clamant demand, while the occult sciences of astrology and alchemy lent their support[.]

Be aware that occult knowledge can be used for good or evil purposes.

Esoteric.

Elbows almost touching they leaned at ease, idly reading the almost obliterated lines engraved there. ¶ "I never understood it," she observed, lightly scornful. "What occult meaning has a sun-dial for the spooney? I'm sure I don't want to read riddles in a strange gentleman's optics."

Supernatural affairs.

Due to my strong personal convictions / I wish to stress / That this record / In no way endorses / A belief in the occult