A heavy fall of snow had disrupted the city's transport system.

disrupted 是动词 disrupt 的过去式，disrupt 由前缀 dis-（表示"分离、破坏"）和拉丁词根 rupt（"打破"）组成，字面意思是"打破原有的状态"，引申为"扰乱、中断"的意思。