There are four essential items in any mans life: pound the pussy, eat some food, good shit, and a nice nap. Pound. Eat. Shit. Nap.
The big four is when you can
hit all those items in a single
day. But it only counts when you
hit all four. You can't count two eats, one shit, and one nap, as a big four. However, once the four are completed in a single
day, you can add on additional items for a Big Five, Big Six, and so on.