Flunk \Flunk\, v. i. [imp. & p. p. Flunked; p. pr. & vb. n. Flunking.]

[Cf. Funk.]

To fail, as on a lesson; to back out, as from an undertaking, through fear.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Flunk \Flunk\, v. t. To fail in; to shirk, as a task or duty. [Colloq. U.S.]

Source: Webster's Revised Unabridged Dictionary (1913)
 

Flunk \Flunk\, n. A failure or backing out; specifically (College cant), a total failure in a recitation. [U.S.]

Source: Webster's Revised Unabridged Dictionary (1913)