roll over基本解释
从滚下， 翻滚， 打滚；折；
roll over英英释义
verb
1. make a rolling motion or turn
e.g. The dog rolled over
2. re-invest (a previous investment) into a similar fund or security
e.g. She rolled over her IRA
3. negociate to repay a loan at a later date for an additional fee
e.g. roll over a loan
