Describing something that is long or tall. Similar to lanky
but with more emphasis on the instability of the object (the word itself conjures images of swaying or buckling). The Empire state building could not be described as wabby as it is VERY stable and has a proportionally thick circumference for its height. A palm tree could be described as wabby. The word can also mean exhausted as in physically unstable/ need to lie down and can be used to describe clumsiness if someone is prone to knocking things over.
"Hugos got proper wabby legs man"
"Im wabbed out mate, im gonna stay in tonight"
"stop wabbing about, you're breaking stuff"