1. The lead or most important female singer in a musical production; such as, an opera: The popular prima donna was rehearsing for the new opera which was to be staged during the summer Opera Festival.
2. A temperamental individual, not necessarily associated with theater, who expects special or exceptional treatment from her colleagues: When Jim was working, he noticed that the office prima donna frequently called in sick on Mondays and she would frequently go home early on Fridays.

Calling someone a prima donna is not an insult if you're talking about an actual opera star; however, if anyone else is called a prima donna it usually means he or she is terribly vain, self centered, or egotistical and such a person may demand special privileges.

3. Etymology: from Italian; literally, "first lady"; from Latin prima (feminine), "first" + domina, "lady".