Cross-eyed describes someone whose eyes point inward toward their nose instead of looking straight ahead in the same direction. When you're cross-eyed, one or both eyes turn inward, making it difficult for both eyes to focus on the same object at the same time.

Some people are born cross-eyed, while others develop it as children when the muscles controlling their eye movements don't work together properly. It's a medical condition called strabismus, and eye doctors can often correct it with special glasses, exercises, or sometimes surgery. Without treatment, being cross-eyed can make it hard to judge distances or see clearly because your brain receives two different images.

People also use “cross-eyed” informally to describe the dizzy, unfocused feeling you get from staring at something too long or too closely. After spending hours reading tiny print or focusing intensely on detailed work, you might say “I'm going cross-eyed” to mean your eyes are tired and having trouble focusing. In cartoons, characters sometimes appear momentarily cross-eyed after getting bonked on the head to show confusion or disorientation, though that's just an exaggerated joke about losing your bearings.