A weak or unreliable support, as in I'd counted on her to help, but she turned out to be a broken reed. The idea behind this idiom, first recorded about 1593, was already present in a mid-15th-century translation of a Latin tract, “Trust not nor lean not upon a windy reed.”
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
How to use broken reed in a sentence
The walls of Cloister-Machern received the poor broken reed, who offered to heaven a heart that was dead to the world.The Life of the Moselle | Octavius Rooke
She stooped to pick up a slim, broken reed that crossed her path, and her face was averted.The Daughter of Anderson Crow | George Barr McCutcheon
I have always told you not to put your trust in a broken reed—alias man.Was It Right to Forgive? | Amelia Edith Huddleston Barr
Even Bridget, under the influence of the upper-housemaid, proved a broken reed to lean upon.
All the time she had felt that Freddie was a broken reed, and such he had proved himself.Jill the Reckless | P. G. (Pelham Grenville) Wodehouse