Veg = vegetable. I don't know any relaxed vegetables, do you? There is no further slang, we're talking about that phylum and form of life which is not animal. It's an noun, it's not slang, it's abbreviated and that's it.
A person can vegetate, which is slang, or a person can be a potato, also slang, but there are many words meaning lazy, and there is new slang every gerneration.
Enough for my first free lesson. For the "out" part, tune in next time.