to get out of my face, go annoy someone else.
when a grenade is talking and being annoying you give her the *hand/ finger movement* and say "ugh scadaddle"!
to leave, that's it just to leave. It just means to go away.
"well I think I'm going to scadaddle, I'll see you later"
to get lost; to piss off.(the latter not meaning to urinate but to technically remove yourself from a person's presence.
if an eager man approaches you(a lady) at a bar and says, "hey there babe" you can reply and say "scadaddle you dumb puff, im not iterested"