Green’s Dictionary of Slang

(US/Can.) in a manner pertaining to a preppie n.

1979		Eble Campus Sl. Mar. 6: preppie [...] Susie always dresses preppie.
1984		Totally True Diaries of an Eighties Roller Queen 🌐 16 Nov. I have an apt. with the Ponderosa manager tomorrow at 2:00. I think I got the job. I dressed preppy to make a good impression.