a factor whose effects cannot be accurately assessed; "human behavior depends on many imponderables" difficult or impossible to evaluate with precision; "such imponderable human factors as aesthetic sensibility
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
An imponderable is something unknown which it is difficult or impossible to estimate or make correct guesses about. They are speculating on the imponderables of the future. something that cannot be exactly measured, judged, or calculated