To flatten means to make something flat by pressing, squashing, or spreading it out. When you flatten a cardboard box for recycling, you're collapsing it so it lies completely flat instead of taking up space. A baker flattens dough with a rolling pin to make it thin and even for cookies or pie crust.

Things can also flatten on their own or through natural forces. A tire flattens when it loses air. A strong wind might flatten a field of wheat, pressing all the stalks down against the ground. Gravity flattens drops of water into puddles when they hit the pavement.

The word works in less physical ways too. When a growth chart flattens, it means the line stops rising as steeply and levels off, showing that growth has slowed. You might hear that inflation has flattened, meaning prices have stopped rising so quickly. In music, when you flatten a note, you lower its pitch by a half step.

Sometimes people use flatten to mean defeat or overwhelm completely, as when a football team flattens its opponent with a lopsided score. The sense of pressing down flat connects all these meanings: whether it's dough, a growth curve, or a competitor, to flatten is to bring something down to a lower, more level state.