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1.
An idiot person who knows better, but does the wrong things just to see, knowing that it’s going to end up badly.
A person causing problems out of spite for sport.
A girl is out w/her friends and spots a male co-worker she hates, and he's w/his shorty, and flirts w/him so he would get in trouble.
Shorty would say.."Get your hands off him - quackadoo!"
by xxgirlcali June 22, 2004
 
2.
Mentally ill.
Rita is quackadoo, because during a restaurant visit, she asked the waitress many times to change her order.
by Ronald Clifford Buckman August 09, 2003