imponderable

That cannot undergo precise evaluation.

Not ponderable; not capable of being weighed; without gravity.

In physics, a thing which has no weight: a term formerly applied to heat, light, electricity, and magnetism, on the supposition that they were material substances, and still used of the hypothetical universal medium, ether.

Not ponderable; without sensible or appreciable weight; incapable of being weighed.

An imponderable substance or body; specifically, in the plural, a name formerly applied to heat, light, electricity, and magnetism, regarded as subtile fluids destitute of weight but in modern science little used.

Not ponderable; without sensible or appreciable weight; incapable of being weighed.

An imponderable substance or body; specifically, in the plural, a name formerly applied to heat, light, electricity, and magnetism.

a factor whose effects cannot be accurately assessed

difficult or impossible to evaluate with precision