If the definition of "transhuman" is given along with a definition of
"transhumanism" and of "posthuman" then there shouldn't be a problem.
The usual procedure, at least among academics, when considering a revised
definition of an accepted term, is to refer to the existing definition.
There's no point in creating a new definition unless some shortcoming is
found with the original. In that spirit, here, again, is my definition:
TRANSHUMANISM: Any philosophy of life (such as extropian philosophy) that
seeks the continuation and acceleration of the evolution of intelligent
life beyond its currently human form and human limitations by means of
science and technology, guided by life-promoting principles and values.
[Max More, 1990]
You might replace "evolution" by "development" if you want to only use
"evolution" in its strict technical contemporary sense of a change in
frequency of alleles. (I say "contemporary" because, of course, "evolution"
had a meaning long before we knew about alleles.)
Max More, Ph.D.
UPDATED WEBSITE: New essays, new photos: http://www.primenet.com/~maxmore
President, Extropy Institute: firstname.lastname@example.org, http://www.extropy.org