Can you please clarify this question? Are you asking for the definition of "Average CPC" or are you asking for the average $ amount that CPC is at for Google Adwords and Yahoo! Search? If it's the latter, that's a ridiculous question with an answer that wouldn't serve anyone. You'd need to clarify the industry and even then, think of the number of keywords possible within that industry. If it's the former, see [adwords.blogspot.com...]