What does the Greek word ksimera mean?

There is no Greek word "ksimera". It's likely a misspelling or a word from a dialect not widely known. The closest possibilities, depending on the intended meaning, might involve:

* Ξημερώματα (ximeromata): This means "dawn" or "early morning hours". This is the most likely candidate if the intended word was close to a time of day.

* A misspelling of a word incorporating the root "ξηρός" (xeros) meaning "dry".

To understand what the intended word was, more context is needed. Where did you encounter this word?