Gagic is used when you want to say that someone is really aggressive. It is a type of guy/girl that always wants to fuck, even if their partner doesn't wants to.
Boy: come on let's fuck (starts to lick her pussy)
Girl: no stop i don't want to fuck with you now you are such a gagic
Boi: oh im so sorry baby for being gagic
Gagic is a more offensive way to say shut up . It is founded by Leonardo Dicaprio in 2002.He said GAGIC and then he said that it means shut up.
boy 1: yo n00b
boy 2: GAGIC
boy 1: (starts crying) MOM HE SAID GAGIC TO ME ITS A BAD WORD!!