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bivallate

bivallate, a.
  (baɪˈvæleɪt, -ət)
  [f. bi-2 + vallate a.]
  Having two encircling ramparts.

1930 Antiquity IV. 198 This ‘bivallate ditch’ is a good example of a type of earthwork found commonly in Wessex. 1936 Proc. Prehist. Soc. II. 216 The enclosure appeared to have been built on to a ditch of the bivallate meandering variety. 1963 G. Daniel in Foster & Alcock Culture & Environment ii. 20 The building of the bivallate and multivallate hillforts of Wales.

Oxford English Dictionary

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