promise someone the moon

promise (one) the moon

To promise one something that cannot be done. Your clients will come to distrust you if you keep promising them the moon.
See also: moon, promise
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

promise someone the moon (or earth)

promise something that is unattainable. British
1998 New Scientist Scientists tend to promise taxpayers the moon, and then not deliver.
See also: moon, promise, someone
Farlex Partner Idioms Dictionary © Farlex 2017
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