seal off

seal off idiom
Also, seal up. Close tightly or barricade to prevent entry or exit. For example, We're sealing off the unused wing of the building, or The jar is tightly sealed up. Dating from the first half of the 1900s, this idiom uses seal in the sense of “close securely,” as one used to do with a seal of wax.

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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