How do I do a "NOT IN" query in Mongo?

This is my document:

{ 
    title:"Happy thanksgiving",
    body: "come over for dinner",
    blocked:[
       {user:333, name:'john'},
       {user:994, name:'jessica'},
       {user:11, name: 'matt'},
    ]
}

What is the query to find all documents that do not have user 11 in "blocked"?