sorehead
1. slang A peevish, irritable, or irascible person. I used to find his dry, sarcastic humor funny before, but lately he's just been an unpleasant sorehead. The boss has been a bit of a sorehead ever since the quarterly financial reports came out. I'd avoid her right now, if you can.
2. slang A disgruntled, petulant, vindictive loser. She's always such a sorehead if she loses that I simply refuse to play with her anymore. You don't have to be such a sorehead just because you lost—Tom played the better game today, that's all.