To close an area or place completely, preventing access or escape
To completely close an area so nobody can get in or out
3 meanings, ordered from most common to least. Color-coded by CEFR level.
To close an area, building, or street completely, preventing anyone from entering or leaving, usually for safety or security
"Police sealed off the street after reports of a suspicious package."
Police sealed off a wide area around the Houses of Parliament.
— The Guardian (approximate), reporting on UK security incidents
To close a section of a building, system, or structure completely to prevent the spread of something harmful
"Firefighters sealed off the ventilation system to stop the smoke from spreading."
(Figurative) To cut off access to information, communication, or opportunity
"The new government sealed off all independent media from the official press briefings."
To seal (close completely) something off from the outside — fairly transparent
To completely close an area so nobody can get in or out
Very common in news reports about emergencies, crime scenes, and military operations. Often used with authorities (police, military) as the subject. The 'off' particle emphasises complete separation or disconnection from the outside.
Natural word combinations native speakers use most often.
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