Define what is meant by a 'vegetarian'?

Ok, me and my friend are having a debate on the definition of a vegetarian. Richie thinks a vegetarian is someone who doesn't eat meat solely for the reason that they don't like the idea of animals being killed whereas I think a vegetarian is just someone who doesn't eat meat for whatever their reasons. i.e. it doesn't necessarily have to be because they don't like the thought of animals being killed.. Can someone settle our debate?