Which term describes a double mast sailing vessel with the mizzen mast located aft of the rubber post?

A yawl is defined by its unique rigging structure, which includes two masts—most notably, the mizzen mast is positioned aft (behind) the main mast and the rudder post. This configuration allows for better balance and handling, especially when sailing downwind. The smaller mizzen sail can help provide additional thrust and stabilization, making it easier for a yawl to navigate in various wind conditions.

In contrast, a sloop is characterized by having a single mast and typically one headsail, while a catamaran features two parallel hulls and is not defined by a mast configuration. A barque is a sailing vessel with three or more masts, where at least the foremast is square-rigged, meaning it does not match the description provided in the question. Thus, the distinctive positioning of the mizzen mast behind the rudder post is what confirms that the correct term for this type of vessel is indeed a yawl.