Unseen or undetected for a long time. That rebel group's operations have been completely off the radar for years—I worry we'll never be able to find them.
看不见或未被发现的很长一段时间。反叛集团的业务已经完全关闭雷达多年,我担心我们将永远无法找到他们。
Mr. Smith has gone off the radar since his wife died, so I'm going to stop by his house this afternoon and check on him.