US informal <美, 非正式>
with obj.
1
- drive with (a car engine) at or above its rated maximum rpm（汽车）全速（或超速）行驶（指发动机以最高安全转速或更高情况下行驶）：
both his engines were redlined now.
现在他的两个发动机都达到了最高安全转速。
2
- refuse (a loan or insurance) to someone because they live in an area deemed to be a poor financial risk拒绝（向住在财政风险大的地区者）提供（贷款或保险）。
2.1
- cancel (a project)勾销, 取消（计划）。
- the maximum number of revolutions per minute for a car engine（汽车发动机）最高每分钟安全转速。
词源
from the use of red as a limit marker, in sense 2 a limit marked out by ringing a section of a map.