1. (Science: mathematics) 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)
3. (Science: mathematics) Plus sign, the sign (_) which denotes addition, or a positive quantity.
Origin: L, more; akin to Gr, and cf. Piu, Pleonasm.