set theory - What is the definition of the $uplus$ symbol?

Hi,
I have what I hope is a very simple question related to unfamiliar notation.
I am looking through a maths paper on a topic related to set theory which contains a symbol,

$uplus$,

and I would like to know how, if at all, it differs from the typical

$cup$

symbol in terms of its meaning.
The context leads me to believe that it does not in fact differ at all but since I don't even know the name of the symbol other than the latex id that I looked up, I can't seem to confirm that suspicion.
Cheers

edit: it seems that the latex renderer also does not know about this obscure symbol 'cupplus' but 'uplus' does work.

edit2: thanks for all the replies! however, since everyone commented rather than providing an answer it seems I cannot grant the coveted 'answer' status to anyone. the disjoint union makes the most sense.