Waistcoat

Which sounds much better than vest.

This time around, the trend works when done in a menswear style, worn loose, and definitely with a shirt underneath. Think Sienna Miller or Kate Moss, not Chippendales dancer.

I'm wearing my Banana Republic version oversized (size 10) with a loose tee underneath, and fine-wale cords. Oxfords complete the Annie Hall-ish ensemble.