WordNet sense 1 (interest on an annual basis deducted in advance on a loan):

discount rate, bank discount

WordNet sense 2 (a refund of some fraction of the amount paid):

rebate

WordNet sense 3 (an amount or percentage deducted):

deduction

WordNet sense 4 (bar from attention or consideration):

dismiss, disregard, ignore, push aside, brush aside

WordNet sense 5 (the act of reducing the selling price of merchandise):

price reduction