Definition of "fossé"

The Major then went with me and Euphemia (Victoria staying at the inn) and showed us what is called the Ditch, being the fossé and ruinous banks of the old castle […] .

1792, James Boswell, in Danziger & Brady (eds.), Boswell: The Great Biographer (Journals 1789–1795), Yale 1989, p. 165

I saw him tied up between two boards, by way of the coffin, which was to be provided by contract; and deposited in the fossé that surrounded our prison […] .

1792, Charlotte Smith, Desmond, Broadview, published 2001, page 146