Webster’s Revised Unabridged Dictionary · 1913
Plus
Plus (plŭs), a. [L., more; akin to Gr. πλείων, πλέων, and E. full. See Full, a., and cf. Più, Pleonasm.]
1. (Math.) More, required to be added; positive, as distinguished from negative; — opposed to minus.
2. Hence, in a literary sense, additional; real; actual.
Success goes invariably with a certain plus or positive power. Emerson.
Plus sign (Math.), the sign (+) which denotes addition, or a positive quantity.