What is that supposed to mean???

Last week a shockingly orange invitation to my 10-year high school reunion arrived.

I look forward to going. The $54* price tag hurts a bit but I'll be there nonetheless**.

Amid all the information on the invitation, here's what has me puzzled:
Dress attire: SMART CASUAL

Smart casual? What the hell does smart casual mean? I have no idea what kind of clothing we're expected to show up wearing.


*$54 for a cash bar, a "heavy hors d'oeuvres buffet and dancing. I think we're getting fleeced.

**Mr. Tonks will likely stay home. I'd love for him to go but over $100 for us to eat meatballs and dance to bad music seems obscene.