In futures or options trading, an unusual market condition in which longer-term contracts carry a lower price than near-term contracts.
(The usual relationship - known as contango - is that longer-term contracts carry a higher price than near-term contracts.)
The extent to which a spot price of a foreign currency plus carrying cost exceeds the forward price.
More generally, any market conditions under which related market prices do not have their usual relationships to one other, potentially creating an arbitrage opportunity.
(Also sometimes known as a 'back price'.)