A metaphoric term to describe a person who has a high opinion of themselves and presents themselves as "All-Knowing" or SDS (Shit Don't Stink). The term has been derived from the idea that the person being called a pumpkin head has so much Ego that their head is swollen up like a pumpkin. One or more people at a job setting could possibly possess such traits to warrant being called a Pumpkin Head.
Jim "Hey John, did you meet the new guy"
John "No, but I heard he's a real Pumpkin head"
Jim "you got that right, suffers from SDS big time"
A nickname which at first seems to be an insult but is actually a term of endearment. The nice round shape of a pumpkin is thought of by some people to be a great way to descirbe someone thus the term pumpkin head. Generally used by a parent to his or her handsome son or beautiful daughter.