When something extreme happens. This could be something good or bad, depending on its use. It doesn't always have to be used in the past tense either.
Joe: "Some guy called me a douche at the club, that's when shit got hefty."
Mike: "Oh man I bet you kicked his ass!"
Joe: "Yup"
Tom: "Hey Joe! You douche."
Joe: "That's it, shit is about to get hefty!"
Mike: "Oh man I bet you kicked his ass!"
Joe: "Yup"
Tom: "Hey Joe! You douche."
Joe: "That's it, shit is about to get hefty!"
by KenzelC April 09, 2010