pledge

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

• noun A solemn binding promise to do, give, or refrain from doing something.
• noun Something given or held as security to guarantee payment of a debt or fulfillment of an obligation.
• noun The condition of something thus given or held.
• noun Delivery of goods or personal property as security for a debt or obligation.
• noun The contract or transaction stipulating or involving such delivery.
• noun A token or sign.
• noun A person who has been accepted for membership in a fraternity or similar organization and has promised to join but has not yet been initiated.
• noun The act of drinking in honor of someone; a toast.
• noun A vow to abstain from alcoholic liquor.
• intransitive verb To offer or guarantee by a solemn binding promise: synonym: promise.
• intransitive verb To bind or secure by a pledge or promise: synonym: devote.
• intransitive verb To deposit as security; pawn.
• intransitive verb To promise to join (a fraternity or similar organization).
• intransitive verb To accept as a prospective member of such an organization.
• intransitive verb To drink a toast to.
• intransitive verb To make a solemn binding promise; swear.
• intransitive verb To drink a toast.

from The Century Dictionary.

• To give as a pledge or pawn; deposit in pawn; deposit or leave in possession of a person as security. See pledge, n.
• To give or formally and solemnly offer as a guaranty or security.
• To bind to something by a pledge, promise, or engagement; engage solemnly: as, to pledge one's self.
• To guarantee the performance of by or as by a pledge.
• To give assurance of friendship to, or promise friendship to, by or in the act of drinking; hence, to drink a health to or with.
• To assure solemnly or in a binding manner; guarantee.
• = Syn. 1-3. To pawn, hypothecate. See plight, verb
• noun In law: A person who goes surety or gives bail for another; especially, a surety whom early English law required of a plaintiff on bringing an action. After a time “John Doe” and “Richard Roe” did duty as such pledges.
• noun A bailment of personal property as a security for some debt or engagement. Story, J.
• noun Anything given or considered as security for the performance of an act; a guaranty.
• noun Figuratively, a child; offspring.
• noun A surety; a hostage.
• noun A formal obligation whereby one voluntarily binds himself to abstain from the use of intoxicating drink.
• noun A token or sign of favor, agreement, etc.
• noun An expression of good will, or a promise of friendship and support, conveyed by drinking together; hence, in a more general sense, the act of drinking together; the drinking of a health.

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

• transitive verb To deposit, as a chattel, in pledge or pawn; to leave in possession of another as security.
• transitive verb To give or pass as a security; to guarantee; to engage; to plight.
• transitive verb obsolete To secure performance of, as by a pledge.
• transitive verb To bind or engage by promise or declaration; to engage solemnly.
• transitive verb To invite another to drink, by drinking of the cup first, and then handing it to him, as a pledge of good will; hence, to drink the health of; to toast.
• noun (Law) The transfer of possession of personal property from a debtor to a creditor as security for a debt or engagement; also, the contract created between the debtor and creditor by a thing being so delivered or deposited, forming a species of bailment; also, that which is so delivered or deposited; something put in pawn.
• noun (Old Eng. Law) A person who undertook, or became responsible, for another; a bail; a surety; a hostage.
• noun A hypothecation without transfer of possession.
• noun Anything given or considered as a security for the performance of an act; a guarantee.
• noun A promise or agreement by which one binds one's self to do, or to refrain from doing, something; especially, a solemn promise in writing to refrain from using intoxicating liquors or the like
• noun A sentiment to which assent is given by drinking one's health; a toast; a health.
• noun (Law) A mortgage. See Mortgage.
• noun (Law) The conveyance of an estate to another for money borrowed, to be held by him until the debt is paid out of the rents and profits.
• noun to keep as security.
• noun to pawn; to give as security.