* Avitus meus: This is a good general term, referring to a male ancestor, and could be used for an uncle. However, it's not as precise as other options.
* Patruus meus: This refers specifically to your father's brother.
* Avunculus meus: This refers specifically to your mother's brother.
Therefore, to be most accurate, you need to specify whether you mean your father's brother or your mother's brother. If you're unsure or don't want to be precise, *avitus meus* is a reasonable, albeit less specific, option.