imponderable (adj)

a factor whose effects cannot be accurately assessed

"human behavior depends on many imponderables"

imponderable (adj)

difficult or impossible to evaluate with precision

"such imponderable human factors as aesthetic sensibility"

imponderable (Noun)

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

imponderable (Adjective)

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