Flooding is a behavioural therapy of phobias that is based on the idea of extinction (the conditioned stimulus no longer brings about a conditioned response).
Rather than exposing a person to their phobicstimulus gradually, a person is exposed to the most frightening situation immediately.
With flooding, a person is unable to avoid (negatively reinforce) their phobia and through continuous exposure, anxiety levels decrease (become extinct).
For example, a person with a phobia of dogs would be placed in a room with a dog. The door is then locked and they stay in the room until they are calm.