noun: (medicine) Initialism of sexually transmitted disease. [(medicine) Any of various diseases that are usually contracted through sexual contact.]
noun: (telephony) Initialism of subscriber trunk dialling or subscriber toll dialing.
noun: Initialism of short-term disability.
noun: Abbreviation of standard. [A level of quality or attainment.]
noun: Abbreviation of standard deviation. [(statistics) A measure of how spread out data values are around the mean, defined as the square root of the variance. Represented with the Greek letter σ (sigma).]
