Movement:
* The children ran across the playground. (Meaning: from one side to the other)
* I walked across the bridge. (Meaning: over the top of something)
Distribution:
* The news spread across the country. (Meaning: throughout a place)
* We discussed the plans across different departments. (Meaning: involving many different groups)
Comparison:
* The differences across the two proposals are significant. (Meaning: comparing items)
* There is a strong contrast across cultures in how people greet each other. (Meaning: comparing different groups)
Other:
* I heard a loud crash across the street. (Meaning: on the other side)
* They met across the table. (Meaning: opposite each other)
* The project will be completed across several stages. (Meaning: over a period of time)
The meaning of "across" depends on the context of the sentence.