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.
Unable to be seen; out of sight; not visible.
Not appearing on the surface.
Apparently, but not actually, offline.
That is ignored by a person.
To make invisible, to invisiblize.