From Longman Dictionary of Contemporary Englishcover letterˈcover ˌletter noun [countable] American English TCMa covering letter
Examples from the Corpus
cover letter• Experts say you should never use more than one page for a cover letter.• Make sure to send a cover letter along with your resume.• The best cover letter is concise.• Inside are what we call involvement devices, like the cover letter and those perforated stamps. 