Basically>Verbally Shitting On Ones Self.
Self-Defication is usually over the top and vastly overkill. Sometimes people with Schizophrenia and bi-polar disorders are prone to this. Note Also Drug addicts are to prone to it.
#2 " Yeah That's Right, I'm A DICK! I Suck yup, suck suck suck huge dick!... I'll go to Mexico and go blow one now! Cya." *door slams behind #2*
#3" What Was That?"
#1" That There is a self-deficate, in active form you'd call it self-defication, basically #2 is going for pity and a nice self-hate session, as most of Emo kind cannot stand being happy"
(Note: the overblown retort and return self-insulting are greater than the initial insult. this signifies a Self-Defication)