nepesností
Nepesností is not a recognized term in standard Czech dictionaries or linguistic literature. In practice, it is usually considered a misspelling or typographical variant of nepřesnost, which means inaccuracy or imprecision.
Etymology and form are unclear for nepesností because pesnost is not an attested Czech root. The prefix
Usage and editorial guidance point to correcting the form to nepřesnost or to the appropriate inflected form
See also: nepřesnost, přesnost, jazyková správnost. If you encounter the word in a text, it is advisable