0 a word or a set of letters and numbers that you can use to get a discount (= a reduction in the usual price) when you buy something, given as a way of encouraging you to buy:
I tried to purchase your book using the code found on the Denver Bargains blog, but it said the promo code had expired.
Please click here to visit the event website. Use promo code BC for a discounted rate of $155.
Enter code CPLX in the promo codes box to get free shipping.