Green’s Dictionary of Slang

bad boy n.

[bad adj. + SE boy]

1. [1920s+] (mainly W.I., Guyn., also bad bwai, bad bwoy) a tearaway, a young criminal; in positive version, a black who rejects the second-class role offered by the dominant white society.

2. [1950s] (US black) a general term of approval, referring both to individuals and to objects.

3. [2000s] (US) anything considered impressive.