flail, v. — Green’s Dictionary of Slang

flail v.

[SE fluster + fail; SE flail, to act energetically but without direction]

(US campus) to fail a test through being flustered or over-pressured.

1989		P. Munro Sl. U. 79: flail 1. to get a failing grade because of being flustered.
1997–2000		College Sl. Research Project (Cal. State Poly. Uni., Pomona) 🌐 Flailin’ (adj.) 1. Performing poorly.