Here's what we know:
* Cats primarily meow to communicate with humans. They've learned that meowing gets our attention and often leads to getting what they want (food, attention, access to outside).
* The tone, pitch, and volume of a meow can vary. A higher-pitched, insistent meow might indicate hunger, while a low, rumbling meow might be a sign of contentment.
* Other vocalizations are more likely to have specific meanings. For instance, purring is often associated with contentment, while hisses and growls are signs of fear or aggression.
In short, there's no definitive "dictionary" of cat meows. Paying attention to the context of the meow, the cat's body language, and other cues will help you understand your feline friend's needs and desires.