Here are some possible interpretations:
* It's a cultural habit: Some cultures have habits that may seem strange to others. Spitting can be a way to clear the throat or express disgust, and it may be more common in some cultures than others.
* They're trying to get your attention: Spitting can be a way to get someone's attention, especially in a noisy environment.
* They're trying to be rude: In some cases, spitting can be an intentional act of rudeness.
It's important to consider the context:
* Where did it happen? Is it a crowded street or a quiet library?
* Was it intentional or accidental? Did they look at you or did it happen by accident?
* What was their body language? Were they smiling or frowning?
If you're unsure, it's always best to err on the side of caution and avoid making assumptions.