Accountability means accepting the consequences for what we do or fail to do. We do not blame others or make excuses; we admit our mistakes and correct them. Even if we cause harm unintentionally, we pay the cost. We act responsibly in all our dealings with others.
An example might be that we yelled at our kids for not doing their homework. We would then approach our children, apologize for our poor behavior, and state that it was unacceptable. We might even tell the children we will not eat dessert that night when they all get it.