Easy answer. Remember that you are in an environment of competitive people who are trying to one-up each other. (Love the corporate world and the even more hypocritical neo-corporate world!) The purpose of saying "business casual" is to weed out those who are foolish enough to fall for the bait and who forget that it's always about looking as-good-as-or-better than others. "Business casual" is a code for "dress better than others, but not flashy". Practical applications: toned down suit jacket or blazer, no khaki, no Hawaiian shirt. No guayabera outside of Latin America and Philippines. Think "going to visit someone in order to borrow a LOT of money".