(preppies)
1.
Preppies are young people, especially in America, who have often been to an expensive private school and who are conventional and conservative in their attitudes, behaviour, and style of dress. (mainly AM)
N-COUNT
2.
If you describe someone or their clothes, attitudes, or behaviour as ~, you mean that they are like a ~. (mainly AM)
I couldn’t believe how straight-looking he was, how ~.
...a ~ collar and tie.
ADJ