Anal orgasm. - is it a thing

So I was with a guy at the weekend and he was very very good at foreplay which is always a major bonus. I think I experienced an anal orgasm but I’m really unsure if that’s actually a thing. I had a dildo in me (static, not moving) and he was orally stimulating my perineum and arse and then I felt so overwhelmingly stimulated . It was nothing like a normal clitoral orgasm and he told me everything was contracting down there. This was a first for me but now I’m questioning whether it was actually just a different type of vaginal/clitoral orgasm. Is it actually a thing?