n (1)大老鼠(small animal with a long tail，like a mouse but larger)[C]：R～s carry very nasty diseases. 老鼠传播严重的疾病。The～s have eaten holes in those bags of flour. 老鼠在那些面袋上咬了许多洞。

(2)卑鄙(不诚实)的人(disloyal person who deserts a cause or his friends in time of trouble)[C](infml)：Oh，you dirty～. 噢，你这个卑鄙小人。

the rat race 疯狂激烈的竞争(infml，derog)：The man decided to withdraw from the～race. 那个人决定退出这种疯狂的竞争。

vi (1)捕鼠(hunt or kill rats)[I](通常go～ting)：The cat went～ting last night. 那只猫昨天夜里捕鼠了。

(2)违约(break an agreement or promise)[I，I+prep(on)](infml)：Aren't you thinking of～ting on the deal? 你不是在想终止这项协议吧? He promised us his help，but he has～ted (on us) at the last minute. 他答应过要帮助我们，但在最后时刻食言了。

(3)出卖，泄密，背叛(give secret information about sb;betray)[I，I+prep(on)](infml)：The police know we're here. Someone must have～ted (on us). 警察知道我们在这里，一定是有人出卖了我们。So you～ted on Gertrude? 所以你就出卖了格特鲁德?〖同〗betray