Transhumanism is a philosophy that is at least two thousand years old. The Ancient transhumanists [20th century Earth] argued that human beings should transform the human condition by developing technologies to greatly enhance human intellectual, physical, and psychological capacities.
What once was speculative philosophy has now become scientific fact. Through the application of advanced technology and genetic engineering, transhumanity has become possible, though access to it is strictly limited. Many in the Imperium bristle at this control.
Thus, Transhumanism today is a political movement that believes that such technology should be spread as widely as possible, not restricted to a select few with the resources, connections, or simple good fortune to be able to obtain it.
For the most part, Transhuman technology is limited to cybernetic physical, mental, or perceptive enhancements. Even that TL 11 tech is highly restricted, however. More advanced tech can offer seemingly supernatural psionic abilities. It is even rumored that new TL 15 Transhuman tech can offer a sort of immortality.
This tech is called the Gilgamesh Rose.