Someone addicted to meth. Usually they are untrustworthy, incureable, and totally not themselves. When one does meth, a profound change occurs. The person is no longer themself, and will now steal anything from anyone to get money for meth, and is often alone due to the extreme paranoia induced by the comedown of the meth. First tweekers start by doing lines, then by smoking meth, then freebasing it, then by straight up injecting it. Once they inject speed, they are officially hopeless tweekers. Generally, when such means are taken to get high, the tweeker is now homeless, and disowned by his/her family, really underweight due to lack of food and sleep, and has a poor facial complexion also due to lack of food and sleep. Often, when tweekers are in such state of despair, they will do anything- and I mean anything- to get their meth. Oftentimes they will suck dick (no matter if it's a dude or a chick) and even get raped up the ass for meth. Sometimes they will sell stolen merchandise for meth. Sometimes they will even mug their own family for meth. They can be that desparate.
"Man, don't let the tweekers into your house. You ain't gonna have anythin left when they leave."
"Up the ass, bitch, or you don't get yo' crank!"