adjective: Abbreviation of singular. [Being only one of a larger population.]
noun: (basketball) Initialism of shooting guard. [(basketball) A guard who is usually the taller of the two guard positions, and sometimes specializes in shooting from outside, particular from beyond the three-point line.]
noun: (sciences) Initialism of specific gravity. [(physics) The ratio of the mass of a substance to that of an equal volume of water at 4°C (or to some other reference substance)]
noun: (philately) Initialism of Stanley Gibbons, stamp dealer and catalogue publisher.
noun: Initialism of Super Girl (“DC Comics superheroine”).