/ mɑːʃ; NAmE mɑːrʃ/ noun
[ C , U ] an area of low land that is always soft and wet because there is nowhere for the water to flow away to :
Cows were grazing on the marshes.
► marshy adjective :
marshy ground / land
••
WORD ORIGIN
Old English mer(i)sc (perhaps influenced by late Latin mariscus marsh), of West Germanic origin.