An over the
top pizza where the topping threatens to fall off in an
avalanche, usually created at (drunken)
make-your-own pizza parties where the goal is to produce the gnarliest, most spectacular-looking pizza.
Dude, check out this pizza I made: it has
cheese, ham, mushrooms, chourico,
tomato, garlic, pepperoni, salami, habanero peppers, artichoke,
chicken (whole), eisbein, peppadews, pineapple, more habanero peppers, and avocado. Oh yeah, and a duck.
Now that's what I call a pizzalanche.