aborted sneeze
When you feel like you are about to sneeze, but the urge disappears when you are already halfway into it. These types of sneezes are not as satisfying as regular sneezes, and often result in embarrassment and/or receipt of the "wtf" look.
I was in class when I made an aborted sneeze. I had tried to hold it back, but it came out anyway. Rather than sounding like "ACHOO", it sounded more like "ACHoasdfgh". After it happened, I just sat there and hung my head in shame.