in ancient Rome, one of the chief magistrates who governed in the absence of the kings, consuls, and emperors.

This power was greatest under the emperors. The chief care of the prefect was the government of the city; as taking cognizance of all crimes committed therein or within a hundred miles thereof. He judged capitally and finally, and even presided in the senate. He had also the superintendence of provisions, building, and navigation.