- Roman initialism for “Senatus Populusque Romanus”, or in the original Roman typography, SENATVSPOPVLVSQVEROMANVS. Latin for “The Senate and The Roman People”.
Usage notes 
In the classical period, this was interpreted as applying (in most cases) to the city of Rome's inhabitants, but occasionally to the entire Roman Empire. In modern times, it continues to carry those connotations, but is also used in modern Italy by the municipal government of Rome.