[mass noun]close observation, especially of a suspected spy or criminal 监视;看守(间谍嫌疑人或疑犯) he found himself put under surveillance by British military intelligence. 他发现自己处于英国军事情报机构监视之下。
语源
early 19th cent.: from French, from sur- 'over' + veiller 'watch' (from Latin vigilare 'keep watch')