I am looking for a word or phrase that is similar in meaning to the "support of a function", but in the context of differential forms.
The "support of a function" is the subset of the domain of a function where the function is non-zero.
In my case, consider the bilinear functional $(dx \wedge dy)$ acting on vector pairs in $xyz$-space.
I would like to say something like, "The support of $(dx \wedge dy)$ is the $xy$ plane.", because the result of the calculation is zero unless both vectors have a no-zero projection on the $xy$-plane.