I sometimes tell people that my gender is 'human'.
I'm (a) genderhuman, attracted to other humans
My partner likes to define herself as 'gender nonchalant', which I love.
If deflecting the question doesn't work then I will say that I was DFAB and thus I've had 'gender:female' experiences, but that is more about how the world experiences me than how I experience myself. I used to call myself an 'oddbod', which still kind of expresses my feelings about it. I did think I was the only one, though. Glad I'm not.
I sometimes think about it as though a recruitment consultant is trying to test whether I have a 'Type A personality' (driven, stressed, ambitious) or a 'Type B personality' (relaxed, reflective etc) when actually I'm neither. I'm an artist, darling!
Or... if someone asks whether you're a 'saver' or a 'splurger' and you reply:
"Let's abolish capitalism."
"For physicists, one billion years is not much different from one second. It's just a number. It's an extremely long number, but I can quantify the process."
Dr Kostya Trachenko, London pitch drop experiment