(what the fuck): WTF is sometimes spelled or written out in the NATO phonetic alphabet: whiskey tango foxtrot. (what the fuck): WTF is not usually considered as offensive as the full expression what the fuck.

Why is WTF a bad word?

WTF normally means what the fuck, but it can also mean why, who, when, where, or even whatever the fuck, because WTF not, and WTF would insist otherwise. (WTF it can mean whether the fuck is hereby resolved.) These alternative uses are less immediately intelligible but usually obvious enough in context.

Is WTF an insult?

WTF is as much a swear as f#ck, or a middle finger. They're symbols that represent the word fuck that can be used without saying the actual word. It might get by a censor, but I wouldn't use wtf in any context where you wouldn't use the word fuck, like in front of your boss, parents or children.