Sentence:  Pungent sweat and heatedly trodden grass, fumes of tea and porter, <WSD>thrum</WSD> of hooves from the paddock, the strikings-up and dyings-down of the band all fused into an extreme for Antonia, whose own senses, boatful, stood up to it. 
Meaning of the word marked with <WSD> tags:  A thrumming sound; a hum or vibration.