To arrange in a stack, or to add to an existing stack.
Please stack those chairs in the corner.
To arrange the cards in a deck in a particular manner.
This is the third hand in a row where you've drawn four of a kind. Someone is stacking the deck!
To take all the money another player currently has on the table.
I won Jill's last $100 this hand; I stacked her!
To deliberately distort the composition of (an assembly, committee, etc.).
The Government was accused of stacking the parliamentary committee.
To crash; to fall.
Jim couldn′t make it today as he stacked his car on the weekend.
To operate cumulatively.
A magical widget will double your mojo. And yes, they do stack: if you manage to get two magical widgets, your mojo will be quadrupled. With three, it will be octupled, and so forth.
To place (aircraft) into a holding pattern.
To collect precious metal in the form of various small objects such as coins and bars.
Arranged in a stack
The plates were stacked waiting to be cleaned.
Having large breasts
That girl at the party was really stacked.
Unfairly constructed, as a stacked deck of cards.
That game is stacked. Don't even try it.