a tweaker is simply a weirdo, from that weird girl who stalks you, the weird witch lady who lives at number 3 to that crazy old guy with the massive beard who rides his bike around all day muttering. its useful to have in the vocab as it can be shouted with no risk of insult to the tweaker in question. by streachin the sylables it can be made into an almost bird like cry. if u like
"oh my god, this guy is a fucking stalker, what a tweaker"
"shit dude, did you see that matey wearin girls clothes, what a tweeker"