someone here said something along the lines of "the meaning of the word gay varies from person to person" , and i'll give you that, i haven't thought of other people's definitions, and i apologize for it.
like the comment above me, my definition of gay is man on man.
and because it has been brought up, here is a quick definition:
man + man = gay
man + woman = straight
woman + woman = lesbian
is important to know that some people might be into gay but not lesbian, and viceversa.
for example some straight men like lesbian but not gay.
now, for futas, how i see it:
futa + man = straight
futa + futa/woman = lesbian
that's my view and i think it's the view a good amount of people tend to have. it's easier to see if you simply view futas as women.
oh, and i' also aware that some people also refer to lesbians with the word gay.
looks like there isn't one straight answer