Dogtooth.

Three teenagers are confined to an isolated country estate that could very well be on another planet. The trio spend their days listening to endless homemade tapes that teach them a whole new vocabulary. Any word that comes from beyond their family abode is instantly assigned a new meaning. Hence 'the sea' refers to a large armchair and 'zombies' are little yellow flowers. Having invented a brother whom they claim to have ostracized for his disobedience, the uber-controlling parents terrorize their offspring into submission.