/seuhr vay"leuhns, -vayl"yeuhns/ , n.
1. a watch kept over a person, group, etc., esp. over a suspect, prisoner, or the like: The suspects were under police surveillance.
2. supervision or superintendence.
[ 1790-1800; surveill ( er ) to watch over ( sur- SUR- 1 + veiller vigilare to watch; see VIGIL) + -ance -ANCE ]