SO: /S·O/, n.

1. (also S.O.) Abbrev. for Significant Other, almost invariably written abbreviated and pronounced /S·O/ by hackers. Used to refer to one’s primary relationship, esp. a live-in to whom one is not married. See MOTAS, MOTOS, MOTSS.

2. [techspeak] The Shift Out control character in ASCII (Control-N, 0001110).