Definitions of jail
a place where people that have been arrested are kept, especially when they are kept for a short period of time
He was found drunk on the streets of Glasgow and spent the night in jail.
(US) a place designed to hold people awaiting trial or who are serving short sentences. Jails are usually run by sheriffs and/or local governments, whereas prisons are operated by state governments and the Federal Bureau of Prisons (BOP) and are designed to hold people convicted of crimes.
She had been in jail six months and was still waiting for the verdict.
(UK) often used as a synonym for prison
The jail terms range from two to four years.