The word grate has several meanings:

1. To shred food into small pieces by rubbing it against a rough surface with sharp holes. When you grate cheese for tacos or pizza, you're scraping it across a metal tool called a grater, turning a solid block into thin shreds. You can also grate vegetables like carrots or potatoes. The motion creates a distinctive scratching sound, and you have to watch your knuckles as the cheese gets smaller.
2. To make a harsh, scraping sound that irritates your ears. Fingernails scraping across a chalkboard can grate on your nerves. A rusty gate might grate when it swings open. When something grates on you, it annoys or bothers you over time, like when your little brother makes the same irritating noise again and again.
3. A framework of metal bars, often used to cover an opening. A drain grate in the street allows rainwater to flow through while keeping large objects from falling in. Prison cells in old movies often show prisoners looking through iron grates. A fireplace grate holds logs while allowing air to flow underneath so the fire burns properly.