An homosexual ; a man who engages as the active partner in anal sex with another man. From "jobby" (faecal solid) + "jab" (to prong or spear). It should be noted that some may consider this term offensive - it is favoured by homophobes due to its low potential for "re-appropriation" by the homosexual community (see example).
The word "Jobby" coming from the Scottish for shit/poo, a "Jobby Jabber" concerns the act of sneaking up behind a friend/foe while pressing both hands together into a "praying" position, then forcibly ramming pointed fingers up the (fully clothed) arse of said friend/foe, shouting "JOBBY JABBER!". Remember to run away to avoid violent repurcussions; laughing is optional.