1.) A spirit of a man killed by a mill accident. He is said to haunt a person if they tread on the same spot that he died. In most cases, it is told that he visits the tent of the camper who walked on his place of death
2.) A term sometimes used to describe a person who lurks and/or creeps.
"Who's coming to our camp tonight?"
"I heard the Boojum is coming tonight!"
"Do you see that boojum character lurking outside the day-care?"