Quanto
A quanto, or "quantity adjusting option", is a derivative in which the underlying exposure is denominated in one currency, but the instrument itself is settled by reference to another currency at a fixed rate determined at the outset of the transaction. Quantos accordingly shield the purchaser from exchange rate fluctuations.
Essentially, a quanto has an embedded currency forward with a variable notional amount. It is that variable notional amount that give the quantity adjusting option its name.