The unavoidable "Mega" chip on a plate of nachos.
The chip is usually laden with cheese and has a majority of the toppings stuck to it. It can consist of one or many chips fused together.
Someone always has to eat it, however when the plate of nachos is worked down to the motherchip, everybody hesitates to see who will grab it. The person who does usually has to apologize for taking it.
"Sorry guys, but I'm going for the motherchip. You snooze you lose."
In a bowl of nachos, The large chip that has all the toppings on it (bean dip, sour cream, salsa) etc. You dip all the bare chips into its toppings. If eaten, you could die from eating all those bare chips.
"Dude you just ruined the nachos!"
"You ate the Mother Chip and all its luscious toppings."
"ohh my bad bro."
"poor bare chips"
That last nacho chip you find at the bottom of the pile with loads of everything on it.
"Man! That's one badass mother-chip. You gonna eat all that?"