m-ing

The act of molesting someone.

Person 1: I love you ( reaching down random person's pants.)
Person 2: Stop m-ing me, dawg.

M f-ing

Basically stands for 'mother fucking'

"Urgh, my m f-ing hammies are ripping in half" - http://www.youtube.com/watch?v=-sr4YqJAuZ4

m-u-ing

pronounced Em-you-ing
Mutual Understanding
used to explain a romantic relationship where two partners are not going out, for whatever reason

Guy 1: hey, dude, is that girl you were with your girlfriend?
Guy 2: umm, no, we're kind of m-u-ing

m-ing

acting up like mya chidi does

did you really just send that picture ?!
you’re m-ing mate ?