Here first are three ways I've heard people use the term outside of an academic context, none of which is very close to what I assume it means here in a college philosophy course. By the way, if you think that philosophy teachers share this conception of academic philosophy, click here for a peek at the grade distributions in this class in some recent semesters. Each of the following conceptions of philosophy has been wide-spread among academic philosophers at some period in the history of Western philosophy. Although hardly a comprehensive survey of the things philosophers have had to say about the nature of their discipline, these three conceptions and how they arose in history illustrate how philosophy as a discipline has evolved and why I, personally, embrace the third one for purposes of teaching a class like this one.
Philosophy is all rational, systematic knowledge.
Philosophy is, or at least should be, limited to the analysis and clarification of language. This conception of philosophy was prominent among a number of anglo-American philosophers during the first half of this century. On this assumption, any question which cannot be answered correctly with a statement which is either a relation of ideas or a matter of fact is a meaningless question. Philosophy is or ought to be the systematic study of certain non-empirical but enduring questions emphasizing clearly stated arguments and analysis of key terms. This final conception of philosophy, which is the one I assume in my classes, describes the attempt to address these enduring questions in a systematic, rational way despite the fact that people have disagreed about the answers to them for millenia.