This is a horrible word - and it's even worse than it looks, because it's actually two words.
There's boil as in the painful bump under the skin, of which nothing good can be said except that it has the splendid synonym furuncle.
There's also boil as when a liquid bubbles and turns into a gas, which I have to admit is more interesting. Boiling happens when gas bubbles form inside a liquid and then bobble their way up to the surface.
The harder the air is pressing down on the liquid, the harder it is for bubbles to form. This means that if the pressure of the air is high, the liquid won't be able to boil until it's at a higher temperature than usual.
This is why the liquid in a high-pressure cooker boils at a higher temperature than in an ordinary saucepan (and so cooks the food faster); why you can't have a decent cup of tea on Everest (there's less air above Everest than anywhere else, so there's less air to press down on the water, which therefore boils more easily (and at a lower temperature) and doesn't brew the tea properly); and why potatoes take longer to cook in thundery weather (thunder happens when the air pressure is low).
Apart from these two meanings, there's a seafood boil. This is, predictably, a sort of party where you boil seafood.
It's probably delicious, but it sounds horrible.
Word Not To Use Today: boil. The furuncle boil comes from the Old English bȳle, the Old Norse beyla, which means swelling, and the Gothic ufbauljan, which means to inflate.
The liquid sort of boil comes from the Old French boillir, and before that from the Latin bullīre, to bubble.