SOS
/ˈesˌəʊˈes/noun
(pl. SOSs)
1- an international code signal of extreme distress, used especially by ships at sea（国际通用的船舶等的）无线电紧急呼救信号。
1.1
- an urgent appeal for help紧急求救。
1.2
- Brit. a message broadcast to an untraceable person in an emergency〈英〉广播紧急找人。
词源
early 20th cent.: letters chosen as being easily transmitted and recognized in Morse code; by folk etymology an abbreviation of save our souls.