What does mega mean in English slang?

Excuse me, could you perhaps enlighten me on the meaning of the term "mega" in contemporary English slang? I've noticed it being used quite frequently in casual conversations and online forums, but I'm not entirely sure what it signifies. Is it a way to express something as being extremely large, impressive, or noteworthy? Or perhaps it has a more nuanced meaning that I'm not aware of? I'd be grateful if you could provide some clarification on this matter.