What does "sign off" mean?
Announce the end of a communication, especially a broadcast. For example, There's no one there now; the station has signed off for the night. [c. 1920]
Stop talking, become silent, as in Every time the subject of marriage came up, Harold signed off. [Colloquial; mid-1900s]
Express approval formally or conclusively, as in The President got the majority leader to sign off on the tax proposal. This usage is colloquial.
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