1. fall back upon：fall back on 求助于; 依靠; 退守; 撤退到...线; 回过来再谈 | fall back upon 求助于; 依靠; 退守; 撤退到...线; 回过来再谈 | fall behind 落后; 跟不上; 拖欠
2. fall back on：fall back 撤退, 后退; 违约, 食言; 达不到目的 | fall back on 求助于; 依靠; 退守; 撤退到...线; 回过来再谈 | fall back upon 求助于; 依靠; 退守; 撤退到...线; 回过来再谈
3. 911查询·英语单词
3. to fall back：to disorganize the defense 破坏防守 | to fall back 退守 | to intercept 截球