A brand of clothing whose name is an abbreviation of the term For Us By Us, meaning the brand was started by black people and its target market is specifically black people.
I worked at a movie theater in Oregon from 1998 to 2000. A co-worker of mine used to live in the San Francisco area, and one time when he was at a party, he saw a black guy with a Fubu shirt that had a hole in the front of it. He asked the guy "What happened to your shirt?" and the black guy answered, completely straight-faced, "A white guy was wearing it. I shot him and took the shirt." A cookie of wisdom for any white people trying to be black -- don't wear Fubu in big cities.