Sentence:  At last, what with a round of blasphemy, and the whole crowd with clay pistols belching smoke and fire and slander of their neighbours, and the floor already <WSD>befouled</WSD> with dregs and spittle, I feared lest viler deeds should happen, and craved to depart. 
Meaning of the word marked with <WSD> tags:  To make foul; to soil; to contaminate, pollute.