NOUN (3)

1. the condition of being serrated;
- Example: "the serrations of a city skyline"

2. a row of notches;
- Example: "the pliers had serrations to improve the grip"

3. a single notch in a row of notches;
- Example: "one of the serrations was broken off"

The Collaborative International Dictionary of English v.0.48:

Serration \Ser*ra"tion\, n.
   1. Condition of being serrate; formation in the shape of a
      saw.
      [1913 Webster]

   2. One of the teeth in a serrate or serrulate margin.
      [1913 Webster]

WordNet (r) 3.0 (2006):

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"