A bastardization of "gorp", like gorp, to gorpo is to mount an individual from behind and push his/her head down repeatedly, while the two individuals enthusiastically twirl their arms in concentric circles. In addition, the "gorpoer" also attempts to grope the "gropoee". Traditionally non-consensual; however, the interpretation and experience depend upon the context.
That rabbit is totally gorpoing that duck, somebody stop it! The rabbit and duck are gorpoing... That's hot.