In connection with futures contracts, it is a short position in a contract that is still not offset or closed. As of expiration, open short contracts would be expected to execute by delivering the underlying asset (e.g, shares of stock) and receiving the price (and necessary amounts) in order to cover the sale of underlying asset.

For example, a trader who has sold, or is short, 500 shares of XYX is said to have an open position in that share. The short position will still be open until the trader delivers the sahre out of its inventory or places an order to buy these shares and gets the the order filled by a market participant (and then delivers the shares to the buyer).