A factor that cannot be anticipated.
An imponderable question.
An imponderable substance or body; specifically, in the plural, a name formerly applied to heat, light, electricity, and magnetism.
Not ponderable; without sensible or appreciable weight; incapable of being weighed.
Difficult or impossible to comprehend or evaluate.
something that causes privation or indicates an absence
causing privation; depriving
consisting in the absence of something; negative
indicating the absence of something