over the edge

over the edge idiom
Insane, as in I think he's gone over the edge. This expression alludes to the edge of sanity. [1920s]

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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