1. Urban roof is one of the components of urban imperviable areas and the roof runoff is an important source of urban nonpoint source pollution.
城市屋面是城市不透水面积的一个重要组成部分，屋面径流是城市非点源污染的一个重要来源。
danci.911chaxun.com
adj
1. not admitting of passage or capable of being affected
e.g. a material impervious to water
someone impervious to argument
Synonym: impervious