The after effects of a 'wet' fart, when a small amount of shit stained liquid passes out at the same time as the gas. This stain causes major irritation and much arse scratching. These 'wet' farts are characterised by a loud sloppy ripping noise.
I don't buy the schmegegge about Morty sleeping with Moira.
His version of the story was pure schmegegge.
The whole schmegegge was made up to get Liz a little bit of attention.