Longman Dictionary of Contemporary English
Wiktionary
n. 1 (context US English) A private school intended to prepare its students to get into prestigious universities. 2 (context British English) A private primary school which prepares its pupils for the http://en.wikipedia.org/wiki/Common_Entrance_Examination most commonly at the age of thirteen, and subsequent entry into public school.
WordNet
n. a private secondary school [syn: preparatory school]
Usage examples of "prep school".
Fortunately, most papers prefer to run stories that include real news, not stuff about some prep school’.
From not fitting at home to not fitting in the Fleet prep school had been a tiny, natural transition.
I'm not going to let them think we're babies of fourteen, just come from some silly prep school.
Because Corfin had been in the Academy prep school, and had a Fleet medical record going back ten years or more.
Billy looked like a small boy left behind by his parents after the first day out from prep school.
O'Malley, and from prep school, from Harvard, and from this old Indian horse trainer I met in Tulsa some years back.