Sorry, my example was a bad one. The actual shape I'm interested in is a trapezoid which I think, theoretically, does not have an aspect ratio defined, but for the purposes of my project I have one defined. If you imagine a trapezoid with the parallel sides oriented vertically, is there a ratio for the parallel sides?
Nor am I. The reason there's a name for the ratio of the length to the width of a rectangle is because TV screens, theater screens, and computer monitors are all rectangular, but can have different aspect ratios. There isn't any similar real-world use for trapezoidal image formats, so it's doubtful anyone has come up with a name.