Business attire to me says "suit" and the accompanying medium-high drag: tie, black shoes, dress shirt. Ugh.
I don't own a suit, but I do have a low end Armani black sports jacket that I got at a rummage sale for $5 and black slacks that came from The Gap or someplace and they sort of match. I have worn them to mandatory dress-up events like funerals and gotten away with it.
Short of a tux, business means more-is-more.
Whenever I do put on this get-up, I make sure to wear festive underwear just to remind myself who I am.
"If my life weren't funny, it would just be true. And that would be unacceptable."
--Carrie Fisher