Definition of: pledge

(plej) v.t. pledged, pledg·ing
1. To give or deposit as security for a loan, etc.; pawn.
2. To bind by or as by a pledge.
3. To promise solemnly, as assistance.
4. To offer (one's word, life, etc.) as a guaranty or forfeit.
5. To drink a toast to.
6. To promise to join (a fraternity).
7. To accept (someone) as a pledge (def. 5). [<noun]
—noun
1. A guaranty for the performance of an act, contract, or duty.
2. A formal promise to do or not to do something; especially, a vow to abstain from intoxicating liquors.
3. The drinking of a health or to good cheer.
4. A pawn of personal property; also, the property delivered.
5. One who has promised to join a fraternity but who has not yet been formally inducted. [<OF plege security, prob. <Gmc.]