i'm close enough to the community to know that "transgendered" is generally not the preferred terminology, erk.
trans/transgender person/man/woman is preferred? though i know a lot of people prefer to just be called simply men or women! since that's what they are!!
anyway, so far as i'm aware of, transgender simply implies that a person's personal gender identity does not match that assigned to them at birth, usually but not always along the binary. of course, neuter/genderqueer/gen derfluid etc. people can fit that description too? but it's under the same umbrella, i suppose.
and 'transitioning' is not a requirement to be trans*, someone is still what they say they are, whether or not they've had sex confirmation surgeries....