slipslipslipsslippedslipping1verb (slips, slipping, slipped)1to move smoothly over something by accident and fall or almost fall: He slipped on the ice and broke his leg.2to go quickly and quietly so that nobody sees you: Ann slipped out of the room. We slipped away when no one was looking.3to put something in a place quickly and quietly: He slipped the money into his pocket.slip up (informal) to make a mistakeslipslipslips2noun1a small mistake: It was just a slip.2a small piece of paper: Write your address on this slip of paper.