a giddy, empty-headed, talkative person.
- rattle off,
Origin of rattlebrain
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for rattlebrain
That was a lot of rattlebrain talk anyway—we're so clevaire!Tom Slade with the Boys Over There|Percy K. Fitzhugh