lock in

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun 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.
• verb To secure someone or something in a locked enclosure.
• verb To fix the value of something potentially variable.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb place in a place where something cannot be removed or someone cannot escape
• verb close with or as if with a tight seal