Moongose is not defined

I got a 500 error and de description says: Mongoose is not defined when i call /delPost, but in the same file "post.js" the functions /addPost and /getPosts are working and use mongoose.model without problems. im a newbie and have searched a lot but can't fix that issue, hope you can help me.

routes/post.js

var express = require('express');
var mongoose = require('mongoose');
var router = express.Router();

POST message to board (WORKING)

router.post('/addPost', function(req, res) {

if(req.body){
    var post = mongoose.model('post');
    var newpost = new post(req.body);
    console.log(newpost);

    newpost.save(function(err, newpost){
        if(err) return res.send(200,{msg: 'not saved'});
    })
    console.log('save ok');
  }
  else{
    res.send(200,{msg: 'no data received'});
  }

});

GET messages from DB to show in HTML (WORKING)

router.get('/getPosts', function(req, res) {
var post = mongoose.model('post');

post.find(function(err, posts){
    if(err) return console.log(err);
    // console.log(posts);
    res.send(posts);
  })  
});

DELETE a post (NOT WORKING)

router.post('/delPost/:rel', function(req, res){

// var mongoose = require('mongoose');
var post = moongose.model('post');


 post.remove({_id: req.params.rel},function(err) {
 if(err) return handleError(err);
 console.log(err);
 })

});

AJAX Call to /delPost route

function delPost(event){
  event.preventDefault();

  console.log('delpost');
  var confirmation = confirm('Are you sure to delete this message?');

  if(confirmation === true){

    $.ajax({
        type:'POST',
        url: '/post/delPost/' + $(this).attr('rel')
    }).done(function(response){
        console.log('delete done.. ');
    }).fail(function(response){
        console.log('delete failed');
    })
}

};