What it says in the title. A lot of small craft in Star Wars start with "T" - T-16, T-47, T-65. Did they ever explain what that stands for? In the U.S. Air Force it stands for "training," but I think we can safely assume from the X-wing that that's not what it is here. (I could have posted this on a more general discussion thread, but it definitely was never explained in movies or TV shows - I figured the only place it would've popped up would be in novels or, more likely, the various technical manuals).