Unsinkable means impossible to sink or make go underwater. A famous example is the Titanic, a massive ocean liner that engineers confidently called unsinkable because of its advanced safety features. The ship had watertight compartments that were supposed to keep it afloat even if parts of the hull were damaged. When the Titanic struck an iceberg in 1912 and sank on its first voyage, the disaster shocked the world partly because people had believed the ship truly couldn't sink.

The word also describes someone with a spirit that refuses to be defeated. When you call someone unsinkable, you mean they bounce back from setbacks and disappointments without giving up. A student who fails a test but studies harder for the next one, or an athlete who loses a competition but keeps training, shows an unsinkable attitude. This meaning captures the idea that while the person might get knocked down temporarily, they won't stay down.

In this second sense, unsinkable is a compliment about character. It suggests resilience, determination, and optimism. An unsinkable person might face difficulties, sadness, or failure, but they don't let those experiences overwhelm them or define who they are.