From German. Meaning "knowing better". And that's exactly what it refers to, like the more common "smart ass" or "wise ass", or even "smart elick" (smart aleck). A besserwisser - or wise ass - is a person, often intellectual, or at least pseudo-intellectual, who thinks he or she has more general knowledge about things than most others. It can be correcting language mistakes in grammar and spelling, or it can be within a specific topic like everything from politics, geography and baseball to history and science - anything you can imagine!
- You know that "bananarama" dude at the Madonna forum? Jeesuz, he's so annoying! Such a besserwisser! Whenever I make the tiniest spelling mistake, he's there immediately to correct me and make me look everything but good. And whenever there's a discussion, he always claims he is the one with the correct answer. Every single time - it never fails! Even though I've caught him in misleading knowledge at least a handful of times!
The same as shaft worthy or fuckable. A shag worthy girl or boy is attractive (pretty, sexy etcetera) enough for you to want to have sexual intercourse with her/him, but most oftenly you wouldn't seriously consider initiating a relationship with her/him. The number of shag worthy babes/hunks usually increase proportionally with your consumption of alcoholic liquid. To be shag worthy doesn't imply you have to be good-looking or sexy, not at all, it simply implies you are capable to have sex with the person in an especially needy situation.
- Mate, how's the party last night? Got laid?
- Euhm, to be honest I didn't have that much of a success with the babes yesterday. But you know, with all that vodka...I finally just grabbed a chick I found shag worthy. It wasn't that bad actually, she even gave me oral sex!
Basically to be politically correct. When you're politically correct - or un-anti-politically non-incorrect - you say what people want to hear and expect of you to say. Your ideas, views and opinions are everything but controversial. You have "dull" opinions, which don't differ from the majority of your local or national society, sometimes even in an international or global context.