This is the 15579th most frequent Polish word.
strażackiego
"Strażackiego" means "firefighter's" or "firefighting" (possessive/adjective form in Polish).
The word 'strażackiego' in this sentence is derived from 'strażacki', which pertains to firefighters, and functions as an adjective describing 'wóz' (vehicle).
Widzieliśmy w akcji wóz strażackiego.
We saw the firefighter's vehicle in action.
Here 'strażackiego' describes 'koszula' (shirt), indicating it belongs to or is associated with a firefighter.
Koszula strażackiego zachowała się dobrze po trudnych akcjach.
The firefighter's shirt remained intact after challenging operations.
In this usage, 'strażackiego' modifies 'sprzętu' (equipment), referring to items meant for firefighting.