The Collaborative International Dictionary of English v.0.48:
minuend \min"u*end\, n. [L. minuendus to be diminished, fr. minuere to lessen, diminish. See Minish.] (Arith.) In the process of subtraction[2], the number from which another number (the subtrahend) is to be subtracted, to find the difference. [1913 Webster +PJC]WordNet (r) 3.0 (2006):
minuend n 1: the number from which the subtrahend is subtracted