We don't have synonyms for tenaillon yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are tenaille, medaillon and taillon.
(n) :
(military, historical) A work constructed on each side of the ravelins to increase their strength, procure additional ground beyond the ditch, or cover the shoulders of the bastions.
(n) :
(military, historical) A work constructed on each side of the ravelins to increase their strength, procure additional ground beyond the ditch, or cover the shoulders of the bastions.