It seems to me there isn't any exact definition, which is understandable since ethics are subjective. But that - and the fact that our society isn't completely in gear when it comes doing the best environmentally and socially - makes consuming mindfully tricky.
Because there is also sustainability, which from every definition I've heard means the intersection of social equality, economic honesty, and environmental consciousness. So which should one shoot for? Uphold your ethics or sustain? Or both? Or do the two overlap? I am still working all that out.
And so I made a list of what buying mindfully means to me. It's by no mean exhaustive, and as I learn more it might evolve. At this point in time though, these are my own guidelines for navigating the world of wearables:
Vegan: No animals were harmed. No feathers, fur, or skin.
Fair trade: The makers were hired by someone else who treated them decently and paid them decently. For this there is a proscribed set of standards.
Second hand/Vintage: Buying something already worn, giving it a second (or maybe third or fourth...) life.
Handmade: This could be interpreted different ways. I take it to mean pieces of clothing that you or an independent person (many of the designers on etsy) made. Could be sewn, knit, crochet, etc.
Environmentally sustainable/conscious: The processes that went into to growing the material and making the garment or accessory were all calculated to be environmentally friendly.
Recycled: A new piece was remade from other pieces or a new piece was made of materials that were once other objects that were previously used. (I'm currently in the process of reading Cradel to Cradel, which makes it apparent that "recycled" isn't as simple a definition as we suppose.)