From my rather limited understanding of this in the current climate, one is transitioned if they are living full time as their gender.
The older terms, which date back to when this kind of thing was called transsexualism, would be more akin to
Post-op - One who has had gender-affirming surgery
Pre-op - One who intends to have gender affirming surgery
Non-op - One who either cannot or has chosen not to have gender affirming surgery
That may be what you're thinking of, Txmxer.
Gingerandhoney can correct me if am misspeaking.
"full" or "partial" transition is used by cisgender population to try and distinguish between the various options a trangender person could choose; it is seen as rather prescriptive by medics, psychologists, and the transgender people themselves to refer to a full transition only if that person had gender-affirming surgery, and partial transition to anyone who did not.
It is as psychologically damaging as "passing" (ie. cisgender people judging on whether that transgender person fits in the mold that the strictly binary and cisheteronormative society decreed a man or a woman should look like).
With the same measuring stick that is then being used to judge transgender people, cisgender, more cisgender people than you think would not pass that same judgement.
In many states and countries that gender-affirming surgery is financially and/or legally unobtainable, and some people simply can not undergo said surgery because of medical conditions.
Would anyone have the guts to call that person "not fully transitioned"?
Fact is, once the transgender person thinks and feels their social and or medical transition it is done; for wahtever reason, even if these are medical, legal, or financial; their transition is done. And that is "full transition"; regardless of which options were picked and not picked.
One transgender person's "done, I am fully transitioned" is not the other's.
The person transitioning will have a seemingly unlimited number of transition options available to them.
I'll stick to the most common of options typically available to transgender women here:
how to present dress/style themselves
changing name (not legally)
changing pronouns (not legally)
changing given name (legally)
changing birth certificate (legally)
And we still haven't reached any medical steps.
now we can add the medical steps:
hormone replacement therapy (only adding female hormones)
hormone replacement therapy (only suppressing male hormones)
hormone replacement therapy (both adding female and suppressing male hormones)
speech therapy
vocal chord surgery
facial hair removal
facial feminisation surgery
breast augmentation
gonadectomy (without gender-affirming surgery)
gender-affirming surgery (including gonadectomy)