To substitute for.
To work as a substitute teacher, especially in primary and secondary education.
To replace (a player) with a substitute.
He never really made a contribution to the match, so it was no surprise when he was subbed at half time.
Less commonly, and often as sub on, to bring on (a player) as a substitute.
He was subbed on half way through the second half, and scored within minutes.
To perform the work of a subeditor or copy editor; to subedit.
To lend.
To subscribe.
(BDSM) To take a submissive role.
To coat with a layer of adhering material; to planarize by means of such a coating.
To prepare (a slide) with a layer of transparent substance to support and/or fix the sample.