As Tom points out a weed is any plant that is growing in a place it is not supposed to be. If I have a tomato plant growing in with my lettuce, it is a weed. Dandelions at one point in time were a food crop, they were imported from Europe, and then went wild.
I agree with Corey. A little of everything you said. Although I really don't care to solve arguments, I sure will if I can help in any way. Do a lot of shopping for things online though and you forgot playing online games with people around the world !