How is a definition paper structured?

In my English Composition two cl, I was given a term, symbolism, to define in a five paragraph essay. Well, I failed it because our teacher didn't bother giving us any examples or tell us how this paper is suppose to argue a point and what point it is suppose to argue. He also gave us an incomplete list of unscholarly sources. Oh great, now I know some of what NOT to look for. This paper required three sources. Popular sources such as webster are not allowed. Even an encyclopedia written by another college isn't scholarly enough. I didn't quite know how to outline the paper. He claimed that I didn't even do any 'real' research. He gave me a chance to revise. Well has anyone ever ran into this delimma? What am I suppose to write about? What are some scholarly sources, other than the Oxford English Dictionary?