Unconfirmed means not yet verified or proven to be true. When something is unconfirmed, people have heard about it or suspect it might be true, but nobody has checked the facts carefully enough to be certain.

If you hear an unconfirmed rumor that school might be canceled tomorrow due to snow, it means people are talking about it, but no official announcement has been made. The rumor could turn out to be true or false. Similarly, a news report might mention unconfirmed reports of an important event, meaning journalists have heard about it but haven't verified the information with reliable sources yet.

Scientists use this word when discussing discoveries that haven't been tested thoroughly. An unconfirmed idea is one that seems possible but needs more evidence and experiments before scientists will accept it as fact.

The opposite is confirmed, which means checked and verified as true. When your dentist appointment gets confirmed, someone has checked the schedule and made sure you're really expected at that time. Until then, it remains unconfirmed: probably happening, but not guaranteed.