1. a rough calculation of the value, number, quantity, or extent of something: "estimations of protein concentrations"Similarestimaterough calculationapproximationeducated/informed guessrough guessevaluationassessmentappraisalinformal:guesstimate
Word Originlate Middle English (originally in the sense ‘comprehension, intuition’, also ‘valuing, a valuation’): from Latin aestimatio(n-), from aestimare ‘determine, appraise’ (see estimate).