Source : Webster's Revised Unabridged Dictionary (1913)

Serration \Ser*ra"tion\, n.
   1. Condition of being serrate; formation in the shape of a
      saw.

   2. One of the teeth in a serrate or serrulate margin.

Source : WordNet®

serration
     n 1: the condition of being serrated; "the serrations of a city
          skyline"
     2: a row of notches; "the pliers had serrations to improve the
        grip"
     3: a single notch in a row of notches; "one of the serrations
        was broken off"