1. a sign indicating the operation of subtraction;
The Collaborative International Dictionary of English v.0.48:
Minus \Mi"nus\ (m[imac]"n[u^]s), a. [L. See Minor, and cf.
Mis- pref. from the French.] (Math.)
Less; requiring to be subtracted; negative; as, a minus
Minus sign (Math.), the sign [-] denoting minus, or less,
prefixed to negative quantities, or quantities to be
subtracted. See Negative sign, under Negative.
WordNet (r) 3.0 (2006):
n 1: a sign indicating the operation of subtraction