arcane

About 0.56 uses per million words.

Meaning

1. adjective Understood by only a few.

   arcane rituals

2. adjective Obscure, mysterious.

   arcane origins

3. adjective Requiring secret or mysterious knowledge to understand.
4. adjective Extremely old (e.g. interpretation or knowledge), and possibly irrelevant.

   an arcane law

Similar words

esoteric cryptic obscure mysterious secret eerie unclear shadowy spooky dark

Often followed by

and knowledge language world or to art rules matters