- The definition of harebrained is something that is reckless or not thought out.
An example of something harebrained is a plan that has no chance of working.
harebrained definition by Webster's New World
adjective
having or showing little sense; reckless, flighty, giddy, rash, etc.
harebrained definition by American Heritage Dictionary
adjective
Foolish; flighty: a harebrained scheme.
Usage Note: The first use of harebrained dates to 1548. The spelling hairbrained also has a long history, going back to the 1500s when hair was a variant spelling of hare. The hair variant was preserved in Scotland into the 18th century, and as a result it is impossible to tell exactly when people began writing hairbrained in the belief that the word means “having a hair-sized brain” rather than “with no more sense than a hare.” While hairbrained continues to be used and confused, it should be avoided in favor of harebrained which has been established as the correct spelling.