Under my bar sink in my basement, there is a very odd trap that is
starting to leak under the sink. I am going to replace it with a new
pvc trap, but i was wondering- what is it called?

It is not a drum trap, as i have seen them. This has an inlet and
outlet parallel to each other, and they go into a figure eight shape,
as seen from above, with a flat bottom and a cleanout on the bottom.

What is this contraption called?

Post a photo

Or remove it and take it to HD, Lowes, et. al. to get a replacement.