降级规则(把节点等的级别下降) collapsing: 瘪听; 夹膜; 虚脱的，萎陷的; 压扁; 折叠bubble collapsing: 膜泡折平collapsing board: 夹模板collapsing cavity: 溃灭空穴collapsing cloud: 坍缩云下载手机词典可随时随地查词查翻译
