1) 1 of the 3 main relationship types, the others being Shawty
Of all 3 Boo is easily the most miss used and misunderstood. Your 'Boo' originally designated "the person you fuck but don't want to be seen with..."
2) desperation fuck-buddy, that one lay you know that you can get, but really don't want to stoop to
"Oh look out son, here comes your Boo." "Oh Shit!!" ((panicked diving behind bushes, crawling for the alley, and running like mad))