What exactly is an asteroid anyway?

An asteroid-comet hybrid??

http://news.discovery.com/space/alien-life-exoplanets/asteroid-comet-hybrid-found-with-surprise-ring-system-15031.htm?utm_source=twitter.com&utm_medium=social&utm_campaign=Mythbusters&hootPostID=1b49302613d566cf70599e493e7b3d67

I also want to recognize my hard-working astronomy club students, who are hard at work at building an electromagnet.