A written promise to pay or forfeit money or perform some act upon the occurrence or nonoccurrence of a specific act or the passage of a specified amount of time. See also indenture. appeal bond. A bond required of the appellant in a civil case to ensure that the appellee's costs will be paid if the appeal is dropped or unsuccessful. bail bond.A bond given to a court by a surety to secure the release of a criminal defendant from incarceration and to guarantee the defendant's future appearance...