chaperone

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A guide or companion whose purpose is to ensure propriety or restrict activity.
• noun An older person who attends and supervises a social gathering for young people.
• noun A person, especially an older or married woman, who accompanies a young unmarried woman in public.
• noun Any of a diverse group of proteins that assist other proteins in intracellular folding or formation of polypeptides without becoming part of the final structure.
• transitive verb To act as chaperone to or for. synonym: accompany.

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

• noun An older person who accompanies other younger people to ensure the propriety of their behaviour, often an older woman accompanying a young woman.
• noun biology A protein that assists the non-covalent folding/unfolding and the assembly/disassembly of other macromolecular structures, but does not occur in these structures when the latter are performing their normal biological functions.
• verb to act as a chaperone

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

• noun one who accompanies and supervises a young woman or gatherings of young people
• verb accompany as a chaperone