The act of chilling with your significant other and continuing to have hardcore sex with them to the point where they disintegrate and spawn at a place of higher elevation
Yo, did you chill uphill with Brianna?
Yeah dude she said she ended up on hieters hill!
The word "chilli", in this popular slang term (especially among scholarly, funny individuals) is commonly used in replacement of the word "business", "grill", "kool-aid", etc.