A subseries of a subseries.

(biblical) Any one of the New Testament Epistles of James, 1 and 2 Peter, 1 John, Jude, and sometimes 2 and 3 John, which are not addressed to specific individuals or Churches.

(organic chemistry) The bicyclic sesquiterpene (4aS,9aS)-2,5,9,9-tetramethyldecahydro-1H-benzo[7]annulene that is the basis of many natural products

(colloquial, jargon) Explicitly and specifically approved by appearing on a whitelist, and therefore having greater access or preference.