Euroclydon is a really, really strong wind that blows across the sea. It's like when you blow really hard on a straw and make a really loud noise, except the wind is blowing over the whole ocean and it's much, much louder.
Sometimes, this wind can be so strong that it can cause big waves and rough conditions for boats and ships that are sailing on the sea. It's kind of like when you're trying to ride your bike and there's a really strong wind blowing against you - it's harder to ride because you have to pedal really hard to make progress.
People have known about euroclydon for a very long time, and in fact it's even written about in an old book called the Bible. In the story, a ship is trying to sail in the middle of a big storm with the euroclydon wind blowing, and it's really scary for the people on board.
So, in summary, euroclydon is a very strong wind that blows over the ocean and can cause difficult conditions for boats and ships trying to sail.