A device for sealing a passage against the escape of gases, especially a U - shaped or S - shaped bend in a drainpipe that prevents the return flow of sewer gas by means of a water barrier.是什么意思_A device for sealing a passage against the escape of gases, especially a U - shaped or S - shaped bend in a drainpipe that prevents the return flow of sewer gas by means of a water barrier.在线翻译_英语_读音_用法_例句