Marshy describes ground that is like a marsh: low, wet, and soft. A marshy field, a marshy path, marshy land — the water has not made a lake, but the earth will not stay firm under your feet. It is an adjective; the place itself is a marsh. After heavy rain, even ordinary grass can feel marshy for a few days, and people will use the word loosely for that too. Though actually, if the ground is only wet for an afternoon, a careful speaker might just say muddy; marshy hints that the wetness belongs to the land, not only to the weather.