1) Blunder 2) Slang for a mistake, error 
[dog] Boo Boo is the world`s smallest dog by height, according to the Guinness Book of World Records. Boo Boo faces competition from Milly, another Chihuahua and Beyonce, a Dachshund-Chihuahua mix but they can not be considered until they are one year old. Boo Boo weathered a challenge from Scooter, a Maltese ...
Boo-boo is slang for a mistake, error.
a stupid or silly mistake; blunder. · a minor injury.