Green’s Dictionary of Slang

tuna n.

[1970s]

1. (US) one who believes themselves to be far more sophisticated than is the reality.

2. (US gay) a homosexual sailor who only takes the passive role in fellatio.

3. (US campus/gay) an attractive man; thus hot tuna! an excl. said on seeing a sexy man.

In compounds

tuna (fish) (n.) [1960s+]

1. (US campus/black) a girlfriend, a woman.

2. (orig. US black) the vagina, both positive and negative.

SE in slang uses

In compounds

tuna taco (n.) [taco, a Mexican cornmeal pancake]

[1990s+] a woman’s genitals; esp. in the context of cunnilingus.

tuna wagon (n.) [its only use would be to convey fish]

[1970s+] (US) an old, decrepit car.