Something modish is fashionable and stylish. It's a-la-mode, or right on top of the latest look. In the 1970s, it was considered modish to wear bell bottoms.
The word modish is a combination of the French mode meaning "fashion" and the suffix -ish meaning "very common." When something is modish, it's all the rage. A swanky restaurant where it's hard to get a table or a boutique selling the newest designer labels are considered modish, or in vogue. Open up the pages of Vogue and you'll be accosted with the latest modish looks.