Sentence:  [Father Roman] had shriven many simple souls on the battlefields of the Republic, kneeling by the dying on hillsides, in the long grass, in the gloom of the forests, to hear the last confession with the smell of gunpowder smoke in his nostrils, the rattle of muskets, the hum and <WSD>spatter</WSD> of bullets in his ears. 
Meaning of the word marked with <WSD> tags:  A burst or series of sounds resembling the sound of droplets hitting a surface.