Defining "Business Casual"

There is one phrase that every job interviewee, new employee, business (wo)man, executive and human resource department dreads:

Business Casual

It strikes fear into the heart of workers and companies alike because the precise meaning eludes us. How much "casual" is still "business"? How much "business" allows an outfit to still be "casual"?

Anne Field wrote a very interesting article about the neverending battle for an appropriate work dress code for Businessweek Lifestyle: What is Business Casual?