1.VerbUsed other than figuratively or idiomatically: To secure (someone or something) in a locked enclosure.
"The dog won't escape now we've locked him in.; The dog won't escape now we've locked him in the kitchen."
2.VerbTo fix the value of (something potentially variable).
"I've locked in a rate of 5%.; I've got a 5% rate locked in."
3.VerbTo prevent (someone or something) from escaping, deteriorating, or switching to an alternative.
"Our new foil packets keep the flavour of the crisps locked in.; Companies find various ways to try to lock in a customer base by preventing the products or services from being fully fungible."
4.VerbTo synchronize (especially a rhythm section) into a groove.
5.VerbTo focus entirely (on something).
"I need to lock in for this exam I'm taking tomorrow.; The missile's path is now locked in."