:For the military definition of sloop see: Sloop-of-war. » For the open learning project see: SLOOP Project. A sloop (from Dutch sloep)'s a sailboat with a fore-and-aft rig and a single mast farther forward than the mast of a cutter. A sloop's fore-triangle's smaller than a cutter's, and unlike a cutter, a sloop usually bends only one headsail, though this distinction isn't definitive; some sloops such as the Friendship Sloop have more than one. Ultimately the position of the mast's the most imp… (More on Sloop)