lock-in

noun

1. A sleepover party, usually held in a public place such as a church or school, in which the participants are not allowed to leave until the next morning.“The youth group will have their annual lock-in this weekend.”
2. An illegal but widely-tolerated invitation-only gathering in a British pub, after the end of licensing hours, to allow regular customers the opportunity to enjoy further drinking time.
3. A situation in which members of an industry have agreed to adopt a certain standard and have retooled their production to meet this standard, thus making it very costly to change to a different standard.