Flustered and pompus, like you would be if someone asked you a question you find incredibly offensive. Happens a lot with teachers and snobby upperclassmen.
Another British bit of fun. Used in "Angus, Thongs, and Full Frontal Snogging" and "Harry Potter and the Goblet of Fire". See snogging.
I asked Mrs. Wenger if she was PMSing, and she got all shirty with me.
The ultimate trifecta and sole purpose in the human life. The goal which only brightest and bravest human souls hope to achieve. Of course... yes... this is in reference to the simultaneous sneeze, fart and burp. Side effects include breathlessness and awe.