Definition of "sub"
A submarine sandwich—a sandwich made on a long bun.
A substitute in a football (soccer) game: someone who comes on in place of another player part way through the game.
Short for subscription: a payment made for membership of a club, etc.
A submissive in BDSM practices.
Short for subtitle.
A subroutine (sometimes one that does not return a value, as distinguished from a function, which does).
To substitute for.
To work as a substitute teacher, especially in primary and secondary education.
(soccer) To replace (a player) with a substitute.
(soccer) Less commonly, and often as sub on, to bring on (a player) as a substitute.
To perform the work of a subeditor or copy editor; to subedit.
To coat with a layer of adhering material; to planarize by means of such a coating.
To prepare (a slide) with an layer of transparent substance to support and/or fix the sample.