From Longman Dictionary of Contemporary Englishpep rallyˈpep ˌrally noun [countable] American EnglishDSDL a meeting at a school before a sports event, when cheerleaders lead the students in encouraging their team to win
Examples from the Corpus
pep rally• This sentiment operates daily, not just at an occasional pep rally or assembly.• The metro editor sent me to cover a soccer team pep rally at Columbia University. 