Refers to partaking in kissing with someone else or sexy texting with someone.
This phrase is normally said when one person is texting or talking to someone they want to get jiggy with.
Can be abreviated to /\ if writing it in a text message.
Pauleen: He text me last night!
Cocker: oh really?!! bit of Muchy Muchy ey ;)
Peggy: yeah definate Muchy Muchy taking place Pauleen!!