nounpl. ar·ca·na or ar·ca·nums
- A deep secret; a mystery.
- often arcana Specialized knowledge or details unknown to or misunderstood by the average person: “a private-equity investor whose specialty was the arcana of the banking industry” (Andrew Ross Sorkin).
- A secret essence or remedy; an elixir.
Origin of arcanumLatin arcānum, from neuter of arcānus, secret; see arcane.