Douglas Harper's Etymology Dictionary
1888, from un- + quantifiable (adj.). Related: Unquantifiably.
Wiktionary
a. Incapable of being quantified or precisely defined mathematically. n. Something that cannot be quantified.
Usage examples of "unquantifiable".
It is a kind of pleasant, almost conversational kind of copulation that gradually moves through a series of almost unquantifiable upticks in pace, each marking a stage in her approach to the climax, until at last he will detect certain unmistakable terminal signals from her, soft staccato moaning sounds, a sudden burst of sweat-slickness along her shoulders, and he will whip himself onward then to the final frenzied strokes, taking his cues from her at every point and letting go in the ultimate moment, finally, of his own carefully governed self-control.
Its unquantifiable and unpredictable, and, as a scientist, that frightens you.