Saggy means drooping, hanging down loosely, or no longer firm and tight. When something is saggy, gravity has pulled it downward so it doesn't hold its original shape anymore.

You'll notice sagging everywhere once you start looking. Old couches get saggy cushions that sink in the middle instead of staying plump and supportive. A balloon that's losing air becomes saggy as it deflates. Pants that are too big might be saggy around the waist and knees. If you don't get enough sleep, you might wake up with saggy, puffy skin under your eyes.

Things sag for different reasons. Fabric stretches out from use and washing. Elastic loses its spring over time. Balloons slowly leak air. Muscles and skin change as bodies age. Even a bookshelf can sag in the middle if it holds too many heavy books for too long.

The word can carry a sense of tiredness or wear. A saggy old couch has been sat on countless times. Saggy jeans have been worn and washed until they've lost their shape. When you describe something as saggy, you're usually pointing out that it used to be firmer, tighter, or more upright than it is now.