foss
- A ditch or moat, especially one that is part of a fortification. nounThe ancient castle was surrounded by a deep foss to deter invaders.Archaeologists discovered the remnants of a foss that once protected the medieval town.
- An obsolete term for a waterfall or cascade. nounThe travelers marveled at the foss as it cascaded down the rocky cliff.In old texts, the river's foss was often described as a natural wonder.