To Pumpkin means to puke on yourself either while drinking or after the fact. Most pumpkin sessions occur unexpectedly, causing the majority of the puke to go on the front of the person's shirt or in whatever cup that person may be holding at the time. While pumpkining may be funny to some, it's really no laughing matter when it happens to you while you're still at the bar and it's only 10:30.
Nicknaming puking, 'to pumpkin' derives from the many images of carved out pumpkins with their guts and seeds spilling out of their mouth, giving the image or impression that they've been served a bit too much.
"We were getting all smacked up with these girls and then Evan proceeded to pumpkin all over himself after taking his 12th jager bomb."
"Woke up this morning still feeling awful, looked for a bucket, but only managed an embarrassing pumpkin on my shirt"
"A partnership for a Pumpkin-free America"
"Whoa screlms, I'm gonna pumpkin if I'm not careful"