This term is a combination of two concepts. The first is the wank
ing motion that people make when something is over the top (a more explicit version of rolling one's eyes). The second is a physiological phenomenon that occurs when a male wank
s off too fast, and the result is thick, and somewhat rubbery. The latter phenomenon implies that the response to the over-the-top nature of the person eliciting the response is very powerful.
Strangers with this kind of honesty make me go a big rubbery one, if you know what I mean.