1. A release of excrement from a faulty or overloaded child's diaper.
2. A term used to describe a fart that has escaped all attempts to keep it contained under a comforter or blanket.
"It was a real nightmare, we had a major containment breach, our boys diaper failed to hold and we had to throw out his pants."
"Hold your nose there's been a containment breach. I could not hold it"