You simply say the words "high 7" instead of actually giving someone a high five whenever you are very stoned or something just totally gnarly happens. Its like a high five but you dont actually do it, you only say it. And its high "7" because you get high 7 days of the week. You would say it right after you pick up a sack of some dank or when you just get done with a bowl of some super fire or something.