chaperon

from The Century Dictionary.

• noun A conductor or guide; escort. Compare def. 4.
• To attend (an unmarried girl or woman) in public: said of an older woman or a married woman.
• noun A hood: a name given to hoods of various shapes at different times.
• noun Specifically A hood or cap worn by the Knights of the Garter when in full dress.
• noun A small shield containing crests, initials, etc., formerly placed on the foreheads of horses which drew the hearse in pompous funerals. Also written chaperonne.
• noun Formerly, one who attended a lady to public places as a guide or protector; a duenna; now, more especially, a married woman who, in accordance with the rules of etiquette, accompanies a young unmarried woman to public places or social entertainments.
• noun In entomology, the clypeus of the head of an insect; the part which supports the labrum or upper lip; the nasus; the epistoma.

from the GNU version of the Collaborative International Dictionary of English.

• noun A hood; especially, an ornamental or an official hood.
• noun A device placed on the foreheads of horses which draw the hearse in pompous funerals.
• noun A matron who accompanies a young lady in public, for propriety, or as a guide and protector.
• transitive verb To attend in public places as a guide and protector; to matronize.

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

• noun An adult who accompanies or supervises one or more young, unmarried men or women during social occasions, usually with the specific intent of preventing some types of social or sexual interactions or illegal behavior.
• verb to accompany, to escort
• verb to mother

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

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