The next word I hate.

MARY SUE
This term originally meant an idealized author-insertation character, specifically in fan-fic. The term comes from a specific parody from the Trek fanzines in the 70s. I guess a lot of teenaged writers were writing about brilliant wonderful teenagers serving on the Enterprise.

"Mary Sue" expanded to mean (maybe) an author insertation character in any type of work.

It also means (according to various sources) any type of audience insertation character, especially an awesome wish-fullfillment type character.

BUT is also means (according to some) any type of character the audience is meant to strongly identify with, idealized or not. In descriptions of what a "Mary Sue" is, one can be a Mary Sue if a character is

Perfect
Slightly flawed
Very flawed

Any type of outsider protaganist is likely a Mary Sue, but so is any type of BMOC leader alpha-male type. Being lonely and being loved are both strong evidence of Sue-ism. Being like the author is clear evidence of being a Mary Sue, and so is being radically different.

To summarize... the following characters are Mary Sues.

Luke Skywalker, Spock, Captain Kirk, Captain Picard, Han Solo, Anakin, PT Obi-Wan, Princess Leia, Padme, Thrawn, Mara Jade, Horatio Hornblower, Maximus from Galdiador, Huey, Duey, and Lewie, Talon Carde, Frodo, Aragorn, Neo, Batman, Leopold Bloom, and James Bond

I propose that the term is meaningless because its original usage was so specific and consequently it's been applied to so many situations, each requiring new and in most cases contradictory layers of explanation on the original usage, that it acually can apply to anything the reviewer doesn't like and wants to dismiss as "Mary Sueism".

This is not to be seen as a defense of any character/work that has been accused of "Mary Sue"ing. Only that the term itself has been manipulated to the point of near-meaninglessness.