| a screen or mat covered with a dark material for shielding a camera lens from excess light or glare. |
| a calculus or concretion found in the stomach or intestines of certain animals, esp. ruminants, formerly reputed to be an effective remedy for poison. |
surveillance sur·veil·lance (sər-vā'ləns)
n.
Close observation of a person or group, especially one under suspicion.
The act of observing or the condition of being observed.
The collection, collation, analysis, and dissemination of data.
A type of observational study that involves continuous monitoring of disease occurrence within a population.