To capsize means to overturn in water, turning upside down or on one's side. When a boat capsizes, it flips over, dumping passengers and cargo into the water. Small sailboats can capsize in strong winds or rough waves when water rushes over one side faster than the crew can react. Canoes often capsize when paddlers lean too far to one side or hit an obstacle like a rock.

Larger ships can capsize too, though it's rarer and more dangerous. Sailors practice capsizing small boats on purpose so they learn how to flip them back upright and climb aboard again. This skill can save lives since knowing how to handle a capsized boat calmly can make a scary situation manageable.

You might hear someone joke that they almost capsized their lunch tray in a crowded cafeteria, using the word playfully to describe nearly spilling everything. But in its true nautical sense, capsizing is a serious event that requires quick thinking, swimming skills, and staying calm when everything literally turns upside down.