Mesh.Clear  

// Draws a simple triangle with UVs

function Start () {
gameObject.AddComponent("MeshFilter");
gameObject.AddComponent("MeshRenderer");
var mesh : Mesh = GetComponent(MeshFilter).mesh;

// Clears all the data that the mesh can contain previously.
mesh.Clear();

mesh.vertices = [Vector3(0,0,0), Vector3(0,1,0), Vector3(1, 1, 0)];
mesh.uv = [Vector2 (0, 0), Vector2 (0, 1), Vector2 (1, 1)];
mesh.triangles = [0, 1, 2];
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
void Start() {
gameObject.AddComponent("MeshFilter");
gameObject.AddComponent("MeshRenderer");
Mesh mesh = GetComponent<MeshFilter>().mesh;
mesh.Clear();
mesh.vertices = new Vector3[] {new Vector3(0, 0, 0), new Vector3(0, 1, 0), new Vector3(1, 1, 0)};
mesh.uv = new Vector2[] {new Vector2(0, 0), new Vector2(0, 1), new Vector2(1, 1)};
mesh.triangles = new int[] {0, 1, 2};
}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

def Start():
gameObject.AddComponent('MeshFilter')
gameObject.AddComponent('MeshRenderer')
mesh as Mesh = GetComponent[of MeshFilter]().mesh
mesh.Clear()
mesh.vertices = (Vector3(0, 0, 0), Vector3(0, 1, 0), Vector3(1, 1, 0))
mesh.uv = (Vector2(0, 0), Vector2(0, 1), Vector2(1, 1))
mesh.triangles = (0, 1, 2)