Here are some examples of words using the prefix "sym-":
* Symmetry: A state of balanced proportions, where two halves are identical.
* Symphony: A musical composition for a large orchestra, where different instruments play together.
* Symbiosis: A relationship between two different species, where both benefit.
* Sympathy: A feeling of shared emotions, especially sorrow.
* Synthesis: The process of combining different parts into a whole.
Therefore, the definition of the prefix "sym-" is "together", "with", "joined", "combined", or "simultaneous".