This is the 1088th most frequent Russian word.
противовоздушной
Anti-aircraft.
Here, 'противовоздушные' is used as an adjective to describe 'системы' (systems), indicating their purpose for countering or defending against aerial threats.
Они установили новые противовоздушные системы для защиты города.
They installed new anti-air systems to protect the city.
Here, 'противовоздушной' serves as an adjective modifying 'техникой' (equipment), specifying its nature being related to countering air attacks.
Мы обучались управлению противовоздушной техникой на специальном полигоне.
We trained in operating anti-aircraft equipment at a special range.
In this context, 'противовоздушной' describes 'обороны' (defense), characterizing it as aimed against aerial threats and attacks.