A prepaid means of purchasing photocopies, found at many university libraries. Instead of putting 10 cents in for every copy you make, you have the option of purchasing a small card at the circulation desk. More expensive cards are a better value in terms of price per copy, provided that you use the card completely: while $8.00 buys you 100 copies (at 8 cents per), you can get a 1000-copy card for $60, or 6 cents per copy.
Like any prepaid thing, the Copicard manufacturers know that many of the copies that are bought will never be used, and so will be profit. Still, some people manage to sell their partially used Copicards shortly before graduation at a discount to fortunate underclassmen.