From Longman Dictionary of Contemporary Englishpreppyprep‧py /ˈprepi/ adjective American English informal SESpreppy clothes or styles are very neat, in a way that is typical of students who go to expensive private schools in the US
Examples from the Corpus
preppy• Where Clinton is rugged and earthy, Gore is clean cut and preppy.• He had a few one-week affairs with preppy college-students.• The general effect resembled the mods of 1964/65 with their preppy look.• Tothe-knee blazers are worn with V-neck sweaters and ties, creating a slightly dangerous, preppy look.• Pasaret's friends describe him as being like a preppy nerd picking a fight in the toughest biker bar in town.Origin preppy (1900-2000) prep (school) 