A verb indicating the end of an event or period of time, or the end of one's participation in something. It can also be used to describe a transition from one type of situation or event to another (e.g., from fantasy to reality, and vice versa).
"This month is going to pumpkin and you're not going to get a bit of work done!" (signifying the end of a period of time)
"Alright already! I'll stay up to play Halo 3, but I'm going to pumpkin in an hour." (signifying end of their participation in the day)
"Look at her! She's going to pumpkin when she see's him outside under a bright streetlight." (signifying a transition from fantasy to reality)