{ 
      name: 'book',
      tags: {
        words: ['abc','123']
        lat: 33,
        long: 22
      }
}

Suppose this can be a document. How do you remove "words" directly from all of the documents within this collection? I would like all of the documents to become without "words":

 { 
      name: 'book',
      tags: {
        lat: 33,
        long: 22
      }
}

Do this: In case your db was 'example'

db.example.update({},{$unset: {words:1}},false,true)

Refer this:

http://www.mongodb.org/display/DOCS/Updating#Updating-%24unset