A wad of money; a stack of cash you keep in your pocket.
Bills can be folded, clipped, held by a rubberband etc. Preferably $100s if you plan on spending.
"Cash in the sweatsocks, check the sweatpocks, got a knot in there the size of an X-Box" - Cam'ron (It's Nothing feat. Hell Rell)
"I go get that paper, a mega fucking watch
I be pullin out knots, that can buy me a, yacht" - Lil' Scrappy (Money in the Bank feat. Young Buck)
"I used to play the block like that, i used to carry knots like that, now i got Black Cards, good credit and such, baby boy, cause i'm all grown up!" - Jay-Z (30 Something) (Kingdom Come)