This is the 4804th most frequent Russian word.
зенитных
"Зенитных" means "anti-aircraft" in English.
The word 'зенитные' here modifies 'прожекторы' and refers to equipment used against aerial attacks.
На крыше здания были установлены зенитные прожекторы.
On the roof of the building, there were installed anti-aircraft searchlights.
In this sentence, 'зенитные' describes 'орудия', indicating military weaponry aimed at targeting threats from the air.
Во время войны зенитные орудия защищали стратегически важные объекты.
During the war, anti-aircraft guns defended strategically important facilities.
Here, 'зенитные' is used metaphorically to describe 'телескопы' focused on observing the zenith or the sky directly above.