In physics the term Wilson loop refers to an observable in gauge field theory given by the holonomy of the given gauge field connection along a fixed curve.
In higher gauge theory one correspondingly has observables given by higher holonomy around higher dimensional manifolds, such as surfaces etc. These are hence sometimes called “Wilson surfaces” etc.
e.g.
Anton Alekseev, Olga Chekeres, Pavel Mnev, Wilson surface observables from equivariant cohomology, JHEP11(2015)093 (arXiv:1507.06343)