Not ponderable; without sensible or appreciable weight; incapable of being weighed.
Difficult or impossible to comprehend or evaluate.
An imponderable question.
A factor that cannot be anticipated.
An imponderable substance or body; specifically, in the plural, a name formerly applied to heat, light, electricity, and magnetism.
Immaterial, supersensual, not physical (more properly, "beyond" that which is physical).
Being an adherent of the philosophy of metaphysics.
Of or pertaining to metaphysics.