An SID was the codename for an emergency involving one of the ships outside Deep Space 9. During an SID, the station's engineering personnel would report to rescue stations.

In 2370, Major Kira Nerys declared an "SID in progress" following the destruction of the Cardassian freighter Bok'Nor. Unfortunately, the freighter was completely destroyed, with the loss of all hands. (DS9: "The Maquis, Part I")

According to the Star Trek Encyclopedia, SID stands for "ship in distress".