A cowslip is a small wild plant with yellow, sweet-smelling flowers. a small European wild plant with sweet smelling yellow flowers. Any of several flowering plants, including (chiefly in British usage) the wild primrose (Primula veris) and (in U.S. usage) the marsh marigold (Caltha palustris). P. veris, once so abundant that it was used freely to make cowslip wine, is now much less common. Both P. veris and C. palustris are used in herbal remedies