Discount; reducing the Interest of money In consideration of prompt payment Also a deduction from a stipulated premium on a policy of insurance, in pursuance of an antecedent contract. Also a deduction or drawback from a stipulated payment, charge, or rate, (as, a rate for the transportation of freight by a railroad,) not taken out in advance of payment, but handed back to the payer after he has paid the full stipulated sum.
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TheLaw.com Law Dictionary & Black's Law Dictionary 2nd Ed.