lose one's marbles

lose (one's) marbles

To be or become mentally deficient, incompetent, or deranged; to become of unsound mind. My poor grandmother started losing her marbles after she had a stroke. I've been so sleep deprived lately that it feels like I've lost my marbles!
See also: lose, marble
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

lose one's marbles

See also: lose, marble
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.

lose one’s marbles

verb
See also: lose, marble
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.
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