Green’s Dictionary of Slang

hard-on n.

1. [late 19C+] (also hardie) an erection.

2. [1940s+] passionate, lustful feelings.

3. [1940s+] an obsession, usu. hostile, aggressive feelings towards.

4. [1940s+] (US) a bad temper, irrespective of gender.

5. [1950s+] (US) used as a term of address, usu. sarcastic and referring to someone’s high self-esteem.

6. [1960s+] (US) a despicable individual, a tough, aggressive person.

7. [1960s+] in fig. use, positive feelings.

8. [1980s+] (US) a difficult task.

In phrases

die with a hard-on (v.)

see under die v.

get a hard-on (v.)

1. [late 19C+] to have an erection.

2. [1940s] (US Und.) to draw a pistol.

3. [1960s] to desire someone.

have a hard-on for (v.)

[1980s+] to dislike (intensely).