from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Informal A student or former student of a preparatory school.
- n. Informal A person whose manner and dress are deemed typical of traditional preparatory schools.
- adj. Of or relating to a preppy or a preparatory school.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. relating to things (such as clothing) that are typical of students at prep schools
prep(aratory school) + -y1.(American Heritage® Dictionary of the English Language, Fourth Edition)
prep + -y, with a doubling of the p to ensure proper pronunciation. (Wiktionary)