A double-breasted coat, cut to form tails at the back while the front was cutaway at the waist. The collar was generally stiff and high-standing with notched lapels. This was standard men’s wear during the Regency, with changes over time in the cut of the waist (straight or curved), the width and notching of the lapels, the fullness of the sleeve, etc.
The image shows a detail of a "Costume Parisien" print from Journal des Dames et des Modes, May 25, 1809. The straight-cut waist was by then more popular than the curved cut of earlier years.