Слово "flak". Англо-русский словарь Мюллера

Captain Black followed the last of them outside to observe with relish the effect of the knowledge upon all of the other officers and enlisted men who were assembling with their helmets, parachutes and flak suits around the four trucks idling in the center of the squadron area.

Oh, God! he kept shrieking with no abatement of terror as the flak thumped and mushroomed all about him.

The men had loved flying behind Yossarian, who used to come barreling in over the target from all directions and every height, climbing and diving and twisting and turning so steeply and sharply that it was all the pilots of the other five planes could do to stay in formation with him, leveling out only for the two or three seconds it took for the bombs to drop and then zooming off again with an aching howl of engines, and wrenching his flight through the air so violently as he wove his way through the filthy barrages of flak that the six planes were soon flung out all over the sky like prayers, each one a pushover for the German fighters, which was just fine with Yossarian, for there were no German fighters any more and he did not want any exploding planes near his when they exploded.