au·tot·o·my 
(ô-tŏtə-mē)
(ô-tŏtə-mē)n.
The spontaneous casting off of a limb or other body part, such as the tail of certain lizards or the claw of a lobster, especially when the organism is injured or under attack.
au′to·tomic (ô′tə-tŏmĭk), au′toto·mous adj.
au·toto·mize′ v.