"Highkey bruh! Look at that ass!" - Homie
"Im tryna smoke yo" - Stoner
"Want some tree?" - Dealer
"Highkey." - Stoner
If we say a painting is "high-key" we mean that most or all of the image is light or pale in value. For example, colours mixed with white, called "pastels" or "tints", are high-key. It's the opposite of "low-key", of course.