English

Adjective

imponderable ‎(comparative more imponderable, superlative most imponderable)

1. Not ponderable; without sensible or appreciable weight; incapable of being weighed.
2. Difficult or impossible to comprehend or evaluate.

Noun

imponderable ‎(plural imponderables)

1. (physics) An imponderable substance or body; specifically, in the plural, a name formerly applied to heat, light, electricity, and magnetism.
2. An imponderable question.

References

• imponderable in The Century Dictionary, The Century Co., New York, 1911
• imponderable in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913