Source : Webster's Revised Unabridged Dictionary (1913)

Decimal \Dec"i*mal\, a. [F. d['e]cimal (cf. LL. decimalis), fr.
   L. decimus tenth, fr. decem ten. See {Ten}, and cf. {Dime}.]
   Of or pertaining to decimals; numbered or proceeding by tens;
   having a tenfold increase or decrease, each unit being ten
   times the unit next smaller; as, decimal notation; a decimal
   coinage.

   {Decimal arithmetic}, the common arithmetic, in which
      numeration proceeds by tens.

   {Decimal fraction}, a fraction in which the denominator is
      some power of 10, as 2/10, 25/100, and is usually not
      expressed, but is signified by a point placed at the left
      hand of the numerator, as .2, .25.

   {Decimal point}, a dot or full stop at the left of a decimal
      fraction. The figures at the left of the point represent
      units or whole numbers, as 1.05.

Decimal \Dec"i*mal\, n.
   A number expressed in the scale of tens; specifically, and
   almost exclusively, used as synonymous with a decimal
   fraction.

   {Circulating}, or {Circulatory}, {decimal}, a decimal
      fraction in which the same figure, or set of figures, is
      constantly repeated; as, 0.354354354; -- called also
      {recurring decimal}, {repeating decimal}, and {repetend}.

Source : WordNet®

decimal
     adj 1: numbered or proceeding by tens; based on ten; "the decimal
            system" [syn: {denary}]
     2: divided by tens or hundreds; "a decimal fraction"; "decimal
        coinage"

decimal
     n 1: a proper fraction whose denominator is a power of 10 [syn: {decimal
          fraction}]
     2: a number in the decimal system