Cross has several meanings:

1. To go from one side to the other. When you cross a street, you move from one side to the other. Explorers crossed oceans to reach new lands. Birds cross thousands of miles during migration. You might cross your fingers for good luck, moving one finger over another.
2. To draw a line through something, usually to show it's wrong or completed. When you cross out a mistake on your paper, you're marking through it with an X or a line. Teachers cross out errors when grading. You might cross items off your shopping list as you find them.
3. To oppose or go against someone. When you cross a powerful person, you disagree with them or do something they don't like. In stories, heroes often have to cross dangerous villains to accomplish their goals. If someone warns, “Don't cross me,” they're saying not to challenge or betray them.
4. A structure made of two lines or pieces that cross each other, and an important religious symbol. The Romans executed some people by fastening them to wooden crosses. Christians use the cross as their central symbol because they believe Jesus died on a cross and rose from the dead.
5. A mixture of two different things. A crossbreed dog has parents of different breeds. Scientists cross different plant varieties to create stronger crops.