1. Something against the law but not really cared about by many, such as lighters for those underage, piranhas, or DYI concerts.
2. Something not against the law but cared about by many, such as rolling papers for those underage, salvia, or phishing.
Katy: And I have two cats, a piranha tank...
Hana: Wait, what? Are those legal?
Katy: Eh, kind of diet-legal. Lots of people have them, and nobody really cares.
Katy: Want a joint? It's salvia.
Hana: That stuffs legal, right?
Katy: Yeah, sort of diet-legal. It is, but the cops would care more about this than my piranhas.
Typically derogatory, a diet relationship has one or both parties only interested in short-term, casual interactions; no strings attached, no accountability, and no responsibility, but still wants to label it as a relationship.
Coined in the Pacific Northwest, it has quickly spread among the Seattle hip-hop community and Tacoma party scene.