vanfoss

from The Collaborative International Dictionary of English v.0.48

Vanfoss \Van"foss`\ (v[a^]n"f[o^]s`), n. [F. avant-foss['e];
   avant before + foss['e] ditch. Cf. {Fosse}.] (Fort.)
   A ditch on the outside of the counterscarp, usually full of
   water.
   [1913 Webster]