If you retrain, or if someone retrains you, you learn new skills, especially in order to get a new job.
例句
Why not retrain for a job which will make you happier?...为什么不接受新的培训，找一份让你更快乐的工作？Union leaders have called upon the government to help retrain workers.工会领导人已经呼吁政府帮助对工人进行再培训。