Someone who is being stupid, or unreasonable. You dont like them at all.
That kid trying to be black, yeah, hes a gunker.
A Gothic/punk raver.
Tend to be underage, wear corset-like tops and/or other revealing clothing (think ripped tutus and tights), and far too much make up. May also enjoy drama and other attention-seeking behaviors, which can often be observed through the over-use of "poor and vulnerable me" story lines.
Wow did you see/hear that (what is presumably but not always a) girl?!? Ugh, what a Gunker!
Some one with one eye that is crossed
That girl is a gunker she has one eye looking at you and the other one is looking for you
A person (specifically a woman) who swallows her partner's ejaculate.
That Britney, she doesn't look like much, but she is a complete gunker.