underreckoning vs underestimation

underreckoning and underestimation both are nouns.

Word	Noun	Adjective	Verb	Adverb
underreckoning	Yes	No	No	No
underestimation	Yes	No	No	No

As nouns, underreckoning and underestimation are synonyms defined as:

underreckoning and underestimation: an estimation that is too low; an estimate that is less than the true or actual value

Other synonyms of underreckoning include underestimate, underrating.

underreckoning (noun)	underestimation (noun)
an estimation that is too low; an estimate that is less than the true or actual value	an estimation that is too low; an estimate that is less than the true or actual value