French, literally "wolf-hole".
trou-de-loup (plural trous-de-loup)
- A pit in the form of an inverted cone or pyramid, constructed as an obstacle to the approach of an enemy, and having a pointed stake in the middle.
Part or all of this entry has been imported from the 1913 edition of Webster’s Dictionary, which is now free of copyright and hence in the public domain. The imported definitions may be significantly out of date, and any more recent senses may be completely missing.
(See the entry for trou-de-loup in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913.)