Other forms: flunked, flunking, flunks
To flunk is to fail a test or a course. Flunk the exam, flunk out, flunk a student.
It is American and informal, and it works both ways: a student flunks a test and a teacher flunks a student. To flunk out is to be thrown off a course for failing. British English says fail, and has no equivalent slang of its own.
1verbflunkTo fail a test or a course.
“If I flunk this exam, I'll have to take the whole course again.”
flunk is a failing.
An alteration of an older word funk, meaning to shrink back in fear, from American college slang of the 1820s.
Alteration of funk#Etymology_3, or perhaps a flinch and funk.
Etymology from Wiktionary, CC BY-SA