(US) A sleepoverparty, 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.
(law) 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.
He was a lunatic drunk and started sing songs that lasted into the early hours of the morning and resulted in many weekend lock-ins in the village pub.