1. Of or pertaining to interactions between two or more African Americans, usually regarding violence or crime. The speakers exhorted the community to renounce black-on-black crime.

2. Completely misleading, invisible, or indecipherable (either intentionally or unintentionally), as of black text printed on a black or dark background. There are pages upon pages of sub-clauses and exceptions in this agreement. The whole thing is rather black on black. I hate these black-on-black warning labels, you can't make out what they're trying to warn you about at all!

3. Of an automobile, having the entire outside color scheme done in black. Some people prefer sports cars with bright, flashy colors, but I prefer mine to be black on black.