A submarine. / A submarine sandwich: a sandwich made on a long bun. / (informal) A substitute, often in sports or teaching.

(US, informal) To substitute for. / (US, informal) To work as a substitute teacher, especially in primary and secondary education. / (Britain, informal, soccer) To replace (a player) with a substitute.

Under.

To coat with a layer of adhering material; to planarize by means of such a coating. / (microscopy) To prepare (a slide) with a layer of transparent substance to support and/or fix the sample.

under, beneath / subsidiary, secondary / almost, nearly

(especially sports) To replace something or take someone's place,

Abbreviation of substitute. / Abbreviation of subaudi.

present participle of sub

A copy editing process.

plural of sub