A cat-ketch is a sailboat

Sailboat

A sailboat or sailing boat is a boat propelled partly or entirely by sails. The term covers a variety of boats, larger than small vessels such as sailboards and smaller than sailing ships, but distinctions in the size are not strictly defined and what constitutes a sailing ship, sailboat, or a...

 that is rigged as both a catboat

Catboat

A catboat , or a cat-rigged sailboat, is a sailing vessel characterized by a single mast carried well forward ....

 and a ketch

Ketch

A ketch is a sailing craft with two masts: a main mast, and a shorter mizzen mast abaft of the main mast, but forward of the rudder post. Both masts are rigged mainly fore-and-aft. From one to three jibs may be carried forward of the main mast when going to windward...

. Specifically, there is larger mast stepped at the very bow

Bow (ship)

The bow is a nautical term that refers to the forward part of the hull of a ship or boat, the point that is most forward when the vessel is underway. Both of the adjectives fore and forward mean towards the bow...

, and a smaller mast further aft. It is different than a standard ketch rig because there is no jib, and the foremost mast is further forward than most ketches. This rig is found on sharpie

Sharpie (boat)

Sharpies are long, narrow sailboats with flat bottoms, extremely shallow draft, centerboards and straight, flaring sides. They are believed to have originated in the New Haven, Connecticut region of Long Island Sound, United States...

s and Sea Pearl 21 sailboats.

External Links:

"Why a Cat Ketch" from B and B Yacht Designs.