Source : Webster's Revised Unabridged Dictionary (1913)

Plus \Plus\, a. [L., more; akin to Gr. ?, ?, and E. full. See
   {Full}, a., and cf. {Pi[`u]}, {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.

Source : WordNet®

plus
     n 1: a useful or valuable quality [syn: {asset}] [ant: {liability}]
     2: the arithmetic operation of summing; calculating the sum of
        two or more numbers; "the summation of four and three
        gives seven"; "four plus three equals seven" [syn: {summation},
         {addition}]

plus
     adj 1: on the positive side or higher end of a scale; "a plus
            value"; "temperature of plus 5 degrees"; "a grade of C
            plus" [ant: {minus}]
     2: involving advantage or good; "a plus (or positive) factor"
        [syn: {positive}]

Source : Free On-Line Dictionary of Computing

PLUS
     
        Late 60's.  Machine-oriented systems language used internally
        by Univac.

plus
     
        +
     
        Common: {ITU-T}: plus; add.  Rare: cross; {INTERCAL}:
        intersection.