I know when the Civic HX first came out - Honda's first CVT car - the S was supposed to stand for sport, since it would permit higher RPM and hold the engine speed higher and accellerate a little quicker. There isn't really a second gear since there's no gears at all. It seems a little weird to call it sport on a car that only has 85 horsepower, but I guess they figured they'd just use that anyway since there's no other good letter to represent higher RPM.