To boil means to heat a liquid until it bubbles vigorously and turns into steam. When water boils at normal air pressure, it reaches 212 degrees Fahrenheit (100 degrees Celsius) and you'll see big bubbles rising rapidly to the surface and bursting. This is different from simmering, where just a few small bubbles break the surface quietly.

Boiling is one of the most important cooking techniques. You boil water to cook pasta, boil eggs for breakfast, or boil potatoes for dinner. Boiling kills many germs and bacteria, which is why people in survival situations are told to boil water before drinking it.

The word can also describe intense emotion or conflict building up. When someone's anger is at a boiling point, they're about to explode. A situation might boil over when tensions get too high, like water bubbling up and spilling out of a pot. When you boil down information, you're reducing it to its most important parts, like how boiling reduces liquid in a pot until only the concentrated essence remains.

As a noun, a boil is a painful, swollen bump on the skin, usually caused by an infection.