preppy /ˈpɹɛ.pi/adjective 1noun 1forms 5 adjective1 •(US) Being or relating to something (such as clothing) that is typical of students at prep schools.I'll pick you up after the party. Let's see, there'll be all that deep preppy conversation, preppy dancing, piles of preppy fun. Party starts at nine, I'll pick you up at nine fifteen. — 1983 noun1 •(US) A student of a prep school. formspreppies · more preppy · preppier · most preppy · preppiest