1. [mid-19C+] to hit hard; often ext. as slug it out.
2. [late 19C] to criticize harshly.
3. [late 19C–1900s] in fig. use, to overcome.
4. [late 19C+] (also slug around) in fig. use, to dispute aggressively; often ext. as slug it out.
5. [1910s–40s] to shoot.
6. [1930s] to kill, to murder.
7. [1940s+] (Aus.) to overcharge.
8. [1940s+] (US) to trudge, to move with an effort, to make an effort; thus slugging adj.
9. in fig. use of sense 1 .
10. [1960s] (US) to apply, to dose.
[1910s+] (US) a rough battle, a hard-hitting contest.
[1950s] (US teen) violent, aggressive.