I propose the following tag definition:
Organic is a label placed on food products and clothing that are produced according to organic farming principles. The exact meaning of organic differs per country and/or certification-scheme, but usually it means produced without the use of artificial fertilizers and artifical pesticides, and with ecological balance, animal welfare and biodiversity in mind.
In the tag wiki we can provide a short list of the larger and more common schemes such as Europe's biological/organic scheme and USDA. Perhaps we can even add something about the main differences between them.