Error while trying to access a Terrain's terrainData.

Looking at the documentation for the [Terrain][1], I can see that there is a variable called terrainData that stores all of the information regarding heightmaps, which I want to access. However, when calling it from a script, I get the error that states that Terrain does not contain a definition for terrainData. Specifically:

Assets/GameAssets/Scripts/TerrainDeformer.cs(48,24): error CS1061: Type 'Terrain' does not contain a definition for 'terrainData' and no extension method 'terrainData' of type 'Terrain' could be found (are you missing a using directive or an assembly reference?)

Why am unable to access this variable? Here's some simple example code where it doesn't work:

 using UnityEngine;
 using System.Collections;
 public class Terrain : MonoBehaviour
 {    
     void Start ()
     {
         Terrain t = new Terrain();
         print(t.terrainData);
     }
 }

Thank you! [1]: http://docs.unity3d.com/Documentation/ScriptReference/Terrain.html