Plain English Meaning
A DPE is an experienced pilot the FAA has officially appointed to give checkrides. When you take your final flight test for a pilot certificate, this is usually the person who tests you and signs off your new certificate.
Full Definition
A Designated Pilot Examiner (DPE) is a private individual appointed by the FAA under 14 CFR Part 183 to conduct practical tests (checkrides) for pilot certificates and ratings on the FAA's behalf. A DPE holds the same authority as an FAA Aviation Safety Inspector for the specific tests they are authorized to give, and may charge a fee for their services.
Context Anchor
You encounter a Designated Pilot Examiner during a practical test, commonly called a , and in instructor discussions about preparing a student for that .