We found one dictionary that defines the word defensive structures:

General (1 matching dictionary)

1. defensive structures: Vocabulary.com

(Note: See defensive_structure as well.)

Definitions from WordNet (defensive structure) ▸ noun:  a structure used for defense ▸ Also see defensive_structure ▸ Words similar to defensive structures ▸ Usage examples for defensive structures ▸ Idioms related to defensive structures ▸ Wikipedia articles (New!) ▸ Words that often appear near defensive structures ▸ Rhymes of defensive structures ▸ Invented words related to defensive structures