To careen means to move forward rapidly while swaying or tilting dangerously from side to side. Picture a grocery cart with a wobbly wheel careening down a parking lot ramp, wobbling wildly as it rolls. A car might careen around a corner too fast, leaning so far it feels like it might tip over. A hockey puck can careen off the boards and shoot across the ice in an unexpected direction.

The word captures both speed and loss of control. When something careens, it's not moving in a straight, steady line. It's lurching, tilting, and veering unpredictably. A skateboarder who hits a crack might go careening across the sidewalk, arms windmilling as they try to stay upright.

You might say a story careens from one crazy event to another, or that your day went careening off course when everything started going wrong at once.