verb

• (US, transitive, intransitive) Of a student, to fail a class; to not pass.
• (US, transitive) Of a teacher, to deny a student a passing grade.
• (US, dated, informal) To shirk (a task or duty).
• To back out through fear. (Commonly in the phrase 'flunk it', the 'it' referring to a specific task avoided; sometimes without specific reference, describing a person's attitude to life in general.)