What is that can note be confined in, or excluded from, vessels, like ordinary fluids, gases, etc.; -- said of the imponderable fluids, heat, light, electricity, etc called?

incoercible — (Physics) That can note be confined in, or excluded from, vessels, like ordinary fluids, gases, etc.; -- said of the imponderable fluids, heat, light, electricity, etc. (Webster's 1913.)