A nick name for any of your Irish friends that have a "Mc" in the front on their name that are always mooching. Bumming cigarettes, beers, food, clothes and just about anything they can mooch. They will most often "forget" their wallet when eating out and have to borrow though never to pay back. They can however be very generous when money is available to them and blow through it immediately which is why they never have anything.
McMooch, I can't believe you forgot your wallet again and need to hold 10.
The friend that never orders anything at Mickey D's for various reasons, (low on cash, diet) but will never hesitate to snatch some fries or ask for a sip of coke
Also means to mooch off someone's McMeal and to overstay one's welcome on the tray
Dennison is so cheap he even asks for handouts when people order off the dollar menu, what a McMooch.
I didn't feel like ordering so I just McMooched off Chris until I was booted from the table