Someone who's spurned has been abandoned or rejected, usually by a romantic interest. If your significant other breaks up with you unexpectedly, you might feel spurned.
It's not easy to be a spurned lover, since the adjective implies total rejection by someone you love. A spurned groom, for example, might wait at the church on his wedding day for a bride who never shows up. The Old English root word of spurned makes this rejection pretty clear: spurnan means "to kick away, reject, scorn, or despise."