Rapping while sucking a dick. It was formed when a man bet his friend that he could out rap him while sucking a dick and the friend didn't want to get out rapped by someone sucking a dick so he also began to suck a dick and rap at the same time.

In order to maintain attention and focus during problem solving, a person may mumble random details related to the task. This can also help to drown out external noise and distraction.

Commonly occurs when software developers are deep in code but surrounded by noise and chatter.

when your pants are so tight you can see a womans lips move

When someone is so inebriated that their texts are garbled, reading like phonetic renderings of a drunken fratboy.

see also, drunk texting

A person finding it difficult to communicate due to having face completely covered in ejaculate.

Term used to describe someone who complains, bitches and moans all the time but does it in a low 'mumbled' voice, and in low, run-on sentences so you can't understand what they are saying.
Usually, but not always, limited to grumpy old men.

A Rap song sung in very low tone or with no character (robot voice) or can barely be understood