sur ‧ veil ‧ lance /səˈveɪləns $ sər-/ BrE AmE noun [uncountable]
[ Date: 1800-1900 ; Language: French ; Origin: surveiller 'to watch over' , from sur- ( ⇨ ↑ surcharge ) + veiller 'to watch' (from Latin vigil ; , ↑ vigil ) ]
1 . when the police, army etc watch a person or place carefully because they may be connected with criminal activities
surveillance of
24-hour surveillance of the building
under surveillance
They were under constant close surveillance day and night.
The suspects were kept under surveillance.
electronic surveillance equipment
2 . when one country watches the military activities of another country to see what they are planning to do:
a surveillance mission
surveillance aircraft
3 . when doctors, health departments etc watch an ill person or watch the development of a disease in a population
under surveillance
Diane was placed under psychiatric surveillance.
• • •
THESAURUS
■ work that a spy does
▪ spying the action of secretly collecting information about a person, country, or organization:
Several embassy officials had been arrested for spying.
▪ espionage spying. Espionage is more formal than spying :
Zakharov was charged with espionage.
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The company carried out a campaign of industrial espionage against its main rival.
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Double agents are quite commonplace in the world of espionage.
▪ surveillance activity in which the police, army, etc watch a person or place carefully because they may be connected with criminal activities:
24-hour surveillance of the building
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The police have had him under surveillance (=have been watching him) for months.
▪ covert operations secret military activities against an enemy:
These planes are used by British Intelligence for covert operations.