This is the 13198th most frequent Russian word.
минометной
"Of a mortar" (related to a mortar weapon).
Here, 'минометной' is an adjective describing the nature of the attack as being conducted using mortars.
Солдаты готовились к минометной атаке.
The soldiers were preparing for a mortar attack.
In this sentence, 'минометной' modifies 'расчёт', specifying that it belongs to a category involving mortars.
Для поддержки был использован минометной расчёт.
A mortar unit was utilized for support.
Here, 'минометной' characterizes the type of shooting as related to the use of mortars.