'lock in' definitions:

Definition of 'lock in'

(from WordNet)
verb
Close with or as if with a tight seal; "This vacuum pack locks in the flavor!" [syn: lock in, seal in]
verb
Place in a place where something cannot be removed or someone cannot escape; "The parents locked her daughter up for the weekend"; "She locked her jewels in the safe" [syn: lock in, lock away, lock, put away, shut up, shut away, lock up]

Synonyms of 'lock in'

From: Moby Thesaurus