An old person. Usually an old man. Usually UK slang, can be used against the younger generation.
"You coming out drinking tonight Matt?"
"No, I'm tired from work. Gonna take a nap and chill"
"Don't be such an old Giffer, come out drinking"
Meaning absolutely dead on your feet. More than tired, more than exhausted and more than knackered/shattered. Another way of saying (f*cking knackered)
I am absolutely Funuckered today. My body won't function.