noun · cattle; ox; yellow cattle (Bos taurus)

老农牵着一头黄牛在耕地。

noun · a person who resells tickets or other items at a high profit

演唱会的票已经卖完了，我只能去向黄牛买。

noun · to fail to show up for an appointment; to break a promise or back out of a plan

他原本答应要来，结果最后还是黄牛了。