Learner's definition of PRISON
1 : a building where people are kept as punishment for a crime or while they are waiting to go to court
— often used before another noun
He was in prison at the time.
If caught, they're all going to prison.
She was sent/sentenced to prison for robbery.
He was released from prison.
He's scheduled to get out of prison next month.
a prison cell
a prison guard
an investigation into prison conditions
an overhaul of the prison system
the prison population
an eight-year prison sentence/term
prison time [=the time someone spends in prison]
2 [count] : a place or situation from which you cannot escape