What is Bill Penal?

Legal Definition
Contracts. A written obligation, by which a debtor acknowledges himself indebted in a certain sum, may one hundred dollars, and for the payment of the debt binds himself in a larger sum, say two hundred dollars. Bills penal do not frequently occur in modern practice; bonds, with conditions, have superseded them. Steph. on Pl. 265, note. See 2 Vent. 198. Bills-penal are sometimes called bills obligatory. Cro. Car. 515; 2 Vent. 106. But a bill obligatory is not necessarily a bill penal. Com. Dig. Obligations, D.
-- Bouviers Law Dictionary
Legal Definition
A written obligation by which a debtor acknowledges himself indebted in a certain sum, and binds himself for the payment thereof, in a larger sum, called a "penalty."
-- Black's Law Dictionary
Legal Definition
A written promise to pay more than one’s debt.
-- Ballentine's Law Dictionary