1. [1920s+] (US, also gun-slammer) a gunman, esp. in the (fictional) ‘Wild West’; thus gun-slinger n.
2. [1960s] (US black) a sexually powerful man.
3. [1990s+] (US campus) a woman who rejects a man’s attentions rudely.
4. [1990s+] an employee dedicated to troubleshooting.
5. [1990s+] an aggressive male; a troublemaker.