Hedge
A hedge is a position opened to offset the risk of another one, so that a loss on one is partly or fully made up by a gain on the other.
Holding 1 BTC and opening a 1 BTC short on futures is a hedge: if Bitcoin falls, the short gains what the holding loses. Hedges are one of the few cases where cross margin can help, because the profit on one side supports the margin of the other.
Learn more: isolated vs cross margin.