Most people define ghetto has being out of the ordinary, and being ill-mannered. Most people also use ghetto when they are talking about Blacks. In America, and probably all across the world, Blacks are considered the "ghetto" race.
Ghetto is actually a section of a city occupied by a minority group who live there especially because of social, economic, or legal pressure.
A sentence using the word "ghetto" to most people would be something like this:
"That house looks hella ghetto",< (messed up/ran down) ,"She got ghetto booty", <(black girls ass/it's big) or something in that nature. Most people use the word "ghetto" as a slang word when they are speaking about blacks.