When you think you smell someone or something that's not really there.
"dude, it's like Adam's sitting right next to me!"
"I think you're having ghost scent"
p1: "I can smell a big poo in our house!"
p2: "Who pooped in our house!"
p1: "srsly, where is that shit!"
p2: "I really have no fuckin' idea!"
p1: ~released dog to track down the shit~
p1: "GODDAMN! I still can smell the shit but my dog can't find that goddamned shit..."
p2: "I guess I will call shit loving furfags to get rid of that ghost scents."