"They wouldn't look twice at him if he couldn't do that Wonky Faint thing -"
"Wronski Feint," said Harry, through gritted teeth.
- this really was too bad of Hermione, since the Wronski Feint is the very opposite of 'wonky' in terms of the dexterity needed to pull it off (GF19)
Unsteady, shaky, unreliable. This might be used to describe something that’s so badly put together that it’s about to fall down.