surveillance /sər-vāˈləns or -lyəns/

1. A watch kept over someone or something, esp over a criminal (and his or her activities) by the police
2. Vigilant supervision
3. Superintendence

surveil or surveille /-vālˈ/ transitive verb (back-formation; US)

To observe, keep under surveillance

• buttered
• buttered eggs
• butterfat
• butterfats
• butterfingered
• butterfingers
• butterfish
• butterfishes
• butterflies
• butterflies in the stomach
• butterfly
• butterfly-bow
• butterfly-bows
• butterfly bush
• butterfly bushes
• butterfly clip
• butterfly clips
• butterfly effect
• butterfly fish
• butterfly fishes
• butterfly flower
• butterfly flowers
• butterfly kiss
• butterfly kisses
• butterfly knife