Sir Thomas Sean Connery said:
Transhumanism is an odd term. I can't for the life of me work out what is trans about it. The humanism I get, but where is the trans?
The better word might be techhuman - the idea is a fusing of technology and biological humanity. The reason why trans was chosen is that there's a risk (or hope, depending on perspective) of humanity "losing itself" or becoming something "beyond humanity", fundamentally separate from nontech humans or "muggles".
The old word for this was cyborg, but technological advances have rendered that term obsolete. A techhuman might wear google glasses for example, which is not part of the definition of cyborg, which focused on the physical rather than the virtual.
A techhuman is a form of artificial intelligence. We consider that the underlying human will always "control" the technology he's fused with, but he could willingly (or not willingly) cede control of himself to the tech. Technology could be made to control human muscle function and produce movement without human control. Perhaps a person wants to browse the internet while walking to his car so engages the WalkMe routine, and can then give his full attention to his "mental" webbrowser or google glasses assisted browser.
Transhumanism is yet another Brave New World. I'm not sure what to make of people brimming with excitement about it, other than to think "this isn't going to end well".